diff --git a/ravenwood/Android.bp b/ravenwood/Android.bp
index 6150343..58cd2e4 100644
--- a/ravenwood/Android.bp
+++ b/ravenwood/Android.bp
@@ -166,6 +166,14 @@
     jarjar_rules: ":ravenwood-services-jarjar-rules",
 }
 
+java_device_for_host {
+    name: "ravenwood-junit-impl-for-ravenizer",
+    libs: [
+        "ravenwood-junit-impl",
+    ],
+    visibility: [":__subpackages__"],
+}
+
 // Separated out from ravenwood-junit-impl since it needs to compile
 // against `module_current`
 java_library {
diff --git a/ravenwood/tools/ravenizer-fake/Android.bp b/ravenwood/tools/ravenizer-fake/Android.bp
deleted file mode 100644
index 7e2c407..0000000
--- a/ravenwood/tools/ravenizer-fake/Android.bp
+++ /dev/null
@@ -1,14 +0,0 @@
-package {
-    // See: http://go/android-license-faq
-    // A large-scale-change added 'default_applicable_licenses' to import
-    // all of the 'license_kinds' from "frameworks_base_license"
-    // to get the below license kinds:
-    //   SPDX-license-identifier-Apache-2.0
-    default_applicable_licenses: ["frameworks_base_license"],
-}
-
-sh_binary_host {
-    name: "ravenizer",
-    src: "ravenizer",
-    visibility: ["//visibility:public"],
-}
diff --git a/ravenwood/tools/ravenizer-fake/ravenizer b/ravenwood/tools/ravenizer-fake/ravenizer
deleted file mode 100755
index 84b3c8e..0000000
--- a/ravenwood/tools/ravenizer-fake/ravenizer
+++ /dev/null
@@ -1,31 +0,0 @@
-#!/bin/bash
-# Copyright (C) 2024 The Android Open Source Project
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-# "Fake" ravenizer, which just copies the file.
-# We need it to add ravenizer support to Soong on AOSP,
-# when the actual ravenizer is not in AOSP yet.
-
-invalid_arg() {
-    echo "Ravenizer(fake): invalid args" 1>&2
-    exit 1
-}
-
-(( $# >= 4 )) || invalid_arg
-[[ "$1" == "--in-jar" ]] || invalid_arg
-[[ "$3" == "--out-jar" ]] || invalid_arg
-
-echo "Ravenizer(fake): copiyng $2 to $4"
-
-cp "$2" "$4"
diff --git a/ravenwood/tools/ravenizer/Android.bp b/ravenwood/tools/ravenizer/Android.bp
new file mode 100644
index 0000000..2892d07
--- /dev/null
+++ b/ravenwood/tools/ravenizer/Android.bp
@@ -0,0 +1,25 @@
+package {
+    // See: http://go/android-license-faq
+    // A large-scale-change added 'default_applicable_licenses' to import
+    // all of the 'license_kinds' from "frameworks_base_license"
+    // to get the below license kinds:
+    //   SPDX-license-identifier-Apache-2.0
+    default_applicable_licenses: ["frameworks_base_license"],
+}
+
+java_binary_host {
+    name: "ravenizer",
+    main_class: "com.android.platform.test.ravenwood.ravenizer.RavenizerMain",
+    srcs: ["src/**/*.kt"],
+    static_libs: [
+        "hoststubgen-lib",
+        "ow2-asm",
+        "ow2-asm-analysis",
+        "ow2-asm-commons",
+        "ow2-asm-tree",
+        "ow2-asm-util",
+        "junit",
+        "ravenwood-junit-impl-for-ravenizer",
+    ],
+    visibility: ["//visibility:public"],
+}
diff --git a/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/Ravenizer.kt b/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/Ravenizer.kt
new file mode 100644
index 0000000..da9c7d9
--- /dev/null
+++ b/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/Ravenizer.kt
@@ -0,0 +1,212 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.platform.test.ravenwood.ravenizer
+
+import com.android.hoststubgen.GeneralUserErrorException
+import com.android.hoststubgen.asm.ClassNodes
+import com.android.hoststubgen.asm.zipEntryNameToClassName
+import com.android.hoststubgen.executableName
+import com.android.hoststubgen.log
+import com.android.platform.test.ravenwood.ravenizer.adapter.TestRunnerRewritingAdapter
+import org.objectweb.asm.ClassReader
+import org.objectweb.asm.ClassVisitor
+import org.objectweb.asm.ClassWriter
+import org.objectweb.asm.util.CheckClassAdapter
+import java.io.BufferedInputStream
+import java.io.BufferedOutputStream
+import java.io.FileOutputStream
+import java.io.InputStream
+import java.io.OutputStream
+import java.util.zip.ZipEntry
+import java.util.zip.ZipFile
+import java.util.zip.ZipOutputStream
+
+/**
+ * Various stats on Ravenizer.
+ */
+data class RavenizerStats(
+    /** Total end-to-end time. */
+    var totalTime: Double = .0,
+
+    /** Time took to build [ClasNodes] */
+    var loadStructureTime: Double = .0,
+
+    /** Total real time spent for converting the jar file */
+    var totalProcessTime: Double = .0,
+
+    /** Total real time spent for converting class files (except for I/O time). */
+    var totalConversionTime: Double = .0,
+
+    /** Total real time spent for copying class files without modification. */
+    var totalCopyTime: Double = .0,
+
+    /** # of entries in the input jar file */
+    var totalEntiries: Int = 0,
+
+    /** # of *.class files in the input jar file */
+    var totalClasses: Int = 0,
+
+    /** # of *.class files that have been processed. */
+    var processedClasses: Int = 0,
+) {
+    override fun toString(): String {
+        return """
+            RavenizerStats{
+              totalTime=$totalTime,
+              loadStructureTime=$loadStructureTime,
+              totalProcessTime=$totalProcessTime,
+              totalConversionTime=$totalConversionTime,
+              totalCopyTime=$totalCopyTime,
+              totalEntiries=$totalEntiries,
+              totalClasses=$totalClasses,
+              processedClasses=$processedClasses,
+            }
+            """.trimIndent()
+    }
+}
+
+/**
+ * Main class.
+ */
+class Ravenizer(val options: RavenizerOptions) {
+    fun run() {
+        val stats = RavenizerStats()
+        stats.totalTime = log.nTime {
+            process(options.inJar.get, options.outJar.get, stats)
+        }
+        log.i(stats.toString())
+    }
+
+    private fun process(inJar: String, outJar: String, stats: RavenizerStats) {
+        var allClasses = ClassNodes.loadClassStructures(inJar) {
+            time -> stats.loadStructureTime = time
+        }
+
+        stats.totalProcessTime = log.iTime("$executableName processing $inJar") {
+            ZipFile(inJar).use { inZip ->
+                val inEntries = inZip.entries()
+
+                stats.totalEntiries = inZip.size()
+
+                ZipOutputStream(BufferedOutputStream(FileOutputStream(outJar))).use { outZip ->
+                    while (inEntries.hasMoreElements()) {
+                        val entry = inEntries.nextElement()
+
+                        if (entry.name.endsWith(".dex")) {
+                            // Seems like it's an ART jar file. We can't process it.
+                            // It's a fatal error.
+                            throw GeneralUserErrorException(
+                                "$inJar is not a desktop jar file. It contains a *.dex file."
+                            )
+                        }
+
+                        val className = zipEntryNameToClassName(entry.name)
+
+                        if (className != null) {
+                            stats.totalClasses += 1
+                        }
+
+                        if (className != null && shouldProcessClass(allClasses, className)) {
+                            stats.processedClasses += 1
+                            processSingleClass(inZip, entry, outZip, allClasses, stats)
+                        } else {
+                            // Too slow, let's use merge_zips to bring back the original classes.
+                            copyZipEntry(inZip, entry, outZip, stats)
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    /**
+     * Copy a single ZIP entry to the output.
+     */
+    private fun copyZipEntry(
+        inZip: ZipFile,
+        entry: ZipEntry,
+        out: ZipOutputStream,
+        stats: RavenizerStats,
+    ) {
+        stats.totalCopyTime += log.nTime {
+            inZip.getInputStream(entry).use { ins ->
+                // Copy unknown entries as is to the impl out. (but not to the stub out.)
+                val outEntry = ZipEntry(entry.name)
+                outEntry.method = 0
+                outEntry.size = entry.size
+                outEntry.crc = entry.crc
+                out.putNextEntry(outEntry)
+
+                ins.transferTo(out)
+
+                out.closeEntry()
+            }
+        }
+    }
+
+    private fun processSingleClass(
+        inZip: ZipFile,
+        entry: ZipEntry,
+        outZip: ZipOutputStream,
+        allClasses: ClassNodes,
+        stats: RavenizerStats,
+    ) {
+        val newEntry = ZipEntry(entry.name)
+        outZip.putNextEntry(newEntry)
+
+        BufferedInputStream(inZip.getInputStream(entry)).use { bis ->
+            processSingleClass(entry, bis, outZip, allClasses, stats)
+        }
+        outZip.closeEntry()
+    }
+
+    /**
+     * Whether a class needs to be processed. This must be kept in sync with [processSingleClass].
+     */
+    private fun shouldProcessClass(classes: ClassNodes, classInternalName: String): Boolean {
+        return TestRunnerRewritingAdapter.shouldProcess(classes, classInternalName)
+    }
+
+    private fun processSingleClass(
+        entry: ZipEntry,
+        input: InputStream,
+        output: OutputStream,
+        allClasses: ClassNodes,
+        stats: RavenizerStats,
+    ) {
+        val cr = ClassReader(input)
+
+        lateinit var data: ByteArray
+        stats.totalConversionTime += log.vTime("Modify ${entry.name}") {
+            val flags = ClassWriter.COMPUTE_MAXS
+            val cw = ClassWriter(flags)
+            var outVisitor: ClassVisitor = cw
+
+            val enableChecker = false
+            if (enableChecker) {
+                outVisitor = CheckClassAdapter(outVisitor)
+            }
+
+            // This must be kept in sync with shouldProcessClass.
+            outVisitor = TestRunnerRewritingAdapter(allClasses, outVisitor)
+
+            cr.accept(outVisitor, ClassReader.EXPAND_FRAMES)
+
+            data = cw.toByteArray()
+        }
+        output.write(data)
+    }
+}
diff --git a/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/RavenizerMain.kt b/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/RavenizerMain.kt
new file mode 100644
index 0000000..ff41818
--- /dev/null
+++ b/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/RavenizerMain.kt
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+@file:JvmName("RavenizerMain")
+
+package com.android.platform.test.ravenwood.ravenizer
+
+import com.android.hoststubgen.LogLevel
+import com.android.hoststubgen.executableName
+import com.android.hoststubgen.log
+import com.android.hoststubgen.runMainWithBoilerplate
+
+/**
+ * Entry point.
+ */
+fun main(args: Array<String>) {
+    executableName = "Ravenizer"
+    log.setConsoleLogLevel(LogLevel.Info)
+
+    runMainWithBoilerplate {
+        val options = RavenizerOptions.parseArgs(args)
+
+        log.i("$executableName started")
+        log.v("Options: $options")
+
+        // Run.
+        Ravenizer(options).run()
+    }
+}
diff --git a/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/RavenizerOptions.kt b/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/RavenizerOptions.kt
new file mode 100644
index 0000000..e85e3be
--- /dev/null
+++ b/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/RavenizerOptions.kt
@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.platform.test.ravenwood.ravenizer
+
+import com.android.hoststubgen.ArgIterator
+import com.android.hoststubgen.ArgumentsException
+import com.android.hoststubgen.SetOnce
+import com.android.hoststubgen.ensureFileExists
+import com.android.hoststubgen.log
+
+class RavenizerOptions(
+    /** Input jar file*/
+    var inJar: SetOnce<String> = SetOnce(""),
+
+    /** Output jar file */
+    var outJar: SetOnce<String> = SetOnce(""),
+) {
+    companion object {
+        fun parseArgs(args: Array<String>): RavenizerOptions {
+            val ret = RavenizerOptions()
+            val ai = ArgIterator.withAtFiles(args)
+
+            while (true) {
+                val arg = ai.nextArgOptional()
+                if (arg == null) {
+                    break
+                }
+
+                fun nextArg(): String = ai.nextArgRequired(arg)
+
+                if (log.maybeHandleCommandLineArg(arg) { nextArg() }) {
+                    continue
+                }
+                try {
+                    when (arg) {
+                        // TODO: Write help
+                        "-h", "--help" -> TODO("Help is not implemented yet")
+
+                        "--in-jar" -> ret.inJar.set(nextArg()).ensureFileExists()
+                        "--out-jar" -> ret.outJar.set(nextArg())
+
+                        else -> throw ArgumentsException("Unknown option: $arg")
+                    }
+                } catch (e: SetOnce.SetMoreThanOnceException) {
+                    throw ArgumentsException("Duplicate or conflicting argument found: $arg")
+                }
+            }
+
+            if (!ret.inJar.isSet) {
+                throw ArgumentsException("Required option missing: --in-jar")
+            }
+            if (!ret.outJar.isSet) {
+                throw ArgumentsException("Required option missing: --out-jar")
+            }
+           return ret
+        }
+    }
+
+    override fun toString(): String {
+        return """
+            RavenizerOptions{
+              inJar=$inJar,
+              outJar=$outJar,
+            }
+            """.trimIndent()
+    }
+}
diff --git a/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/Utils.kt b/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/Utils.kt
new file mode 100644
index 0000000..0018648
--- /dev/null
+++ b/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/Utils.kt
@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.platform.test.ravenwood.ravenizer
+
+import com.android.hoststubgen.asm.ClassNodes
+import com.android.hoststubgen.asm.findAnyAnnotation
+import org.objectweb.asm.Type
+
+val junitTestMethodType = Type.getType(org.junit.Test::class.java)
+val junitRunWithType = Type.getType(org.junit.runner.RunWith::class.java)
+
+val junitTestMethodDescriptor = junitTestMethodType.descriptor
+val junitRunWithDescriptor = junitRunWithType.descriptor
+
+val junitTestMethodDescriptors = setOf<String>(junitTestMethodDescriptor)
+val junitRunWithDescriptors = setOf<String>(junitRunWithDescriptor)
+
+/**
+ * Returns true, if a test looks like it's a test class which needs to be processed.
+ */
+fun isTestLookingClass(classes: ClassNodes, className: String): Boolean {
+    // Similar to  com.android.tradefed.lite.HostUtils.testLoadClass(), except it's more lenient,
+    // and accept non-public and/or abstract classes.
+    // HostUtils also checks "Suppress" or "SuiteClasses" but this one doesn't.
+    // TODO: SuiteClasses may need to be supported.
+
+    val cn = classes.findClass(className) ?: return false
+
+    if (cn.findAnyAnnotation(junitRunWithDescriptors) != null) {
+        return true
+    }
+    cn.methods?.forEach { method ->
+        if (method.findAnyAnnotation(junitTestMethodDescriptors) != null) {
+            return true
+        }
+    }
+    if (cn.superName == null) {
+        return false
+    }
+    return isTestLookingClass(classes, cn.superName)
+}
diff --git a/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/adapter/TestRunnerRewritingAdapter.kt b/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/adapter/TestRunnerRewritingAdapter.kt
new file mode 100644
index 0000000..c539908
--- /dev/null
+++ b/ravenwood/tools/ravenizer/src/com/android/platform/test/ravenwood/ravenizer/adapter/TestRunnerRewritingAdapter.kt
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.platform.test.ravenwood.ravenizer.adapter
+
+import com.android.hoststubgen.asm.ClassNodes
+import com.android.hoststubgen.visitors.OPCODE_VERSION
+import com.android.platform.test.ravenwood.ravenizer.isTestLookingClass
+import org.objectweb.asm.ClassVisitor
+
+/**
+ * Class visitor to rewrite the test runner for Ravenwood
+ *
+ * TODO: Implement it.
+ */
+class TestRunnerRewritingAdapter(
+    protected val classes: ClassNodes,
+    nextVisitor: ClassVisitor,
+) : ClassVisitor(OPCODE_VERSION, nextVisitor) {
+   companion object {
+       /**
+        * Returns true if a target class is interesting to this adapter.
+        */
+       fun shouldProcess(classes: ClassNodes, className: String): Boolean {
+            return isTestLookingClass(classes, className)
+       }
+    }
+}
diff --git a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/Exceptions.kt b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/Exceptions.kt
index 910bf59..f59e143 100644
--- a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/Exceptions.kt
+++ b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/Exceptions.kt
@@ -15,6 +15,8 @@
  */
 package com.android.hoststubgen
 
+import java.io.File
+
 /**
  * We will not print the stack trace for exceptions implementing it.
  */
@@ -49,4 +51,22 @@
 /**
  * We use this for general "user" errors.
  */
-class HostStubGenUserErrorException(message: String) : Exception(message), UserErrorException
+class GeneralUserErrorException(message: String) : Exception(message), UserErrorException
+
+/** Base exception class for invalid command line arguments. */
+open class ArgumentsException(message: String?) : Exception(message), UserErrorException
+
+/** Thrown when the same annotation is used with different annotation arguments. */
+class DuplicateAnnotationException(annotationName: String?) :
+    ArgumentsException("Duplicate annotation specified: '$annotationName'")
+
+/** Thrown when an input file does not exist. */
+class InputFileNotFoundException(filename: String) :
+    ArgumentsException("File '$filename' not found")
+
+fun String.ensureFileExists(): String {
+    if (!File(this).exists()) {
+        throw InputFileNotFoundException(this)
+    }
+    return this
+}
diff --git a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenErrors.kt b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenErrors.kt
index 6b01d48..a218c55 100644
--- a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenErrors.kt
+++ b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenErrors.kt
@@ -19,6 +19,6 @@
     open fun onErrorFound(message: String) {
         // TODO: For now, we just throw as soon as any error is found, but eventually we should keep
         // all errors and print them at the end.
-        throw HostStubGenUserErrorException(message)
+        throw GeneralUserErrorException(message)
     }
 }
\ No newline at end of file
diff --git a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenLogger.kt b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenLogger.kt
index fcdf824..4bcee40 100644
--- a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenLogger.kt
+++ b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenLogger.kt
@@ -89,6 +89,8 @@
         addPrinter(StreamPrinter(level, PrintWriter(BufferedOutputStream(
             FileOutputStream(logFilename)))))
 
+        log.i("Log file set: $logFilename for $level")
+
         return this
     }
 
@@ -122,6 +124,9 @@
     }
 
     fun println(level: LogLevel, message: String) {
+        if (message.isEmpty()) {
+            return // Don't print an empty message.
+        }
         printers.forEach {
             if (it.logLevel.ordinal >= level.ordinal) {
                 it.println(level, indent, message)
@@ -185,31 +190,45 @@
         println(LogLevel.Debug, format, *args)
     }
 
-    inline fun <T> logTime(level: LogLevel, message: String, block: () -> T): T {
+    inline fun <T> logTime(level: LogLevel, message: String, block: () -> T): Double {
+        var ret: Double = -1.0
         val start = System.currentTimeMillis()
         try {
-            return block()
+            block()
         } finally {
             val end = System.currentTimeMillis()
+            ret = (end - start) / 1000.0
             if (isEnabled(level)) {
                 println(level,
                     String.format("%s: took %.1f second(s).", message, (end - start) / 1000.0))
             }
         }
+        return ret
     }
 
-    inline fun <T> iTime(message: String, block: () -> T): T {
+    /** Do an "i" log with how long it took. */
+    inline fun <T> iTime(message: String, block: () -> T): Double {
         return logTime(LogLevel.Info, message, block)
     }
 
-    inline fun <T> vTime(message: String, block: () -> T): T {
+    /** Do a "v" log with how long it took. */
+    inline fun <T> vTime(message: String, block: () -> T): Double {
         return logTime(LogLevel.Verbose, message, block)
     }
 
-    inline fun <T> dTime(message: String, block: () -> T): T {
+    /** Do a "d" log with how long it took. */
+    inline fun <T> dTime(message: String, block: () -> T): Double {
         return logTime(LogLevel.Debug, message, block)
     }
 
+    /**
+     * Similar to the other "xTime" methods, but the message is not supposed to be printed.
+     * It's only used to measure the duration with the same interface as other log methods.
+     */
+    inline fun <T> nTime(block: () -> T): Double {
+        return logTime(LogLevel.Debug, "", block)
+    }
+
     inline fun forVerbose(block: () -> Unit) {
         if (isEnabled(LogLevel.Verbose)) {
             block()
@@ -253,6 +272,21 @@
             }
         }
     }
+
+    /**
+     * Handle log-related command line arguments.
+     */
+    fun maybeHandleCommandLineArg(currentArg: String, nextArgProvider: () -> String): Boolean {
+        when (currentArg) {
+            "-v", "--verbose" -> setConsoleLogLevel(LogLevel.Verbose)
+            "-d", "--debug" -> setConsoleLogLevel(LogLevel.Debug)
+            "-q", "--quiet" -> setConsoleLogLevel(LogLevel.None)
+            "--verbose-log" -> addFilePrinter(LogLevel.Verbose, nextArgProvider())
+            "--debug-log" -> addFilePrinter(LogLevel.Debug, nextArgProvider())
+            else -> return false
+        }
+        return true
+    }
 }
 
 private interface LogPrinter {
diff --git a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenMain.kt b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenMain.kt
index 45e7e30..8506466 100644
--- a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenMain.kt
+++ b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenMain.kt
@@ -24,20 +24,32 @@
  */
 fun main(args: Array<String>) {
     executableName = "HostStubGen"
+    runMainWithBoilerplate {
+        // Parse the command line arguments.
+        var clanupOnError = false
+        try {
+            val options = HostStubGenOptions.parseArgs(args)
+            clanupOnError = options.cleanUpOnError.get
 
+            log.v("$executableName started")
+            log.v("Options: $options")
+
+            // Run.
+            HostStubGen(options).run()
+        } catch (e: Throwable) {
+            if (clanupOnError) {
+                TODO("Remove output jars here")
+            }
+            throw e
+        }
+    }
+}
+
+inline fun runMainWithBoilerplate(realMain: () -> Unit) {
     var success = false
-    var clanupOnError = false
 
     try {
-        // Parse the command line arguments.
-        val options = HostStubGenOptions.parseArgs(args)
-        clanupOnError = options.cleanUpOnError.get
-
-        log.v("$executableName started")
-        log.v("Options: $options")
-
-        // Run.
-        HostStubGen(options).run()
+        realMain()
 
         success = true
     } catch (e: Throwable) {
@@ -45,9 +57,6 @@
         if (e !is UserErrorException) {
             e.printStackTrace(PrintWriter(log.getWriter(LogLevel.Error)))
         }
-        if (clanupOnError) {
-            TODO("Remove output jars here")
-        }
     } finally {
         log.i("$executableName finished")
         log.flush()
diff --git a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenOptions.kt b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenOptions.kt
index 2f833a8..f88b107 100644
--- a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenOptions.kt
+++ b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/HostStubGenOptions.kt
@@ -17,20 +17,17 @@
 
 import com.android.hoststubgen.filters.FilterPolicy
 import java.io.BufferedReader
-import java.io.File
 import java.io.FileReader
 
 /**
  * A single value that can only set once.
  */
-class SetOnce<T>(
-        private var value: T,
-) {
+open class SetOnce<T>(private var value: T) {
     class SetMoreThanOnceException : Exception()
 
     private var set = false
 
-    fun set(v: T) {
+    fun set(v: T): T {
         if (set) {
             throw SetMoreThanOnceException()
         }
@@ -39,6 +36,7 @@
         }
         set = true
         value = v
+        return v
     }
 
     val get: T
@@ -59,6 +57,16 @@
     }
 }
 
+class IntSetOnce(value: Int) : SetOnce<Int>(value) {
+    fun set(v: String): Int {
+        try {
+            return this.set(v.toInt())
+        } catch (e: NumberFormatException) {
+            throw ArgumentsException("Invalid integer $v")
+        }
+    }
+}
+
 /**
  * Options that can be set from command line arguments.
  */
@@ -113,18 +121,11 @@
 
         var apiListFile: SetOnce<String?> = SetOnce(null),
 
-        var numShards: SetOnce<Int> = SetOnce(1),
-        var shard: SetOnce<Int> = SetOnce(0),
+        var numShards: IntSetOnce = IntSetOnce(1),
+        var shard: IntSetOnce = IntSetOnce(0),
 ) {
     companion object {
 
-        private fun String.ensureFileExists(): String {
-            if (!File(this).exists()) {
-                throw InputFileNotFoundException(this)
-            }
-            return this
-        }
-
         private fun parsePackageRedirect(fromColonTo: String): Pair<String, String> {
             val colon = fromColonTo.indexOf(':')
             if ((colon < 1) || (colon + 1 >= fromColonTo.length)) {
@@ -137,7 +138,7 @@
         fun parseArgs(args: Array<String>): HostStubGenOptions {
             val ret = HostStubGenOptions()
 
-            val ai = ArgIterator(expandAtFiles(args))
+            val ai = ArgIterator.withAtFiles(args)
 
             var allAnnotations = mutableSetOf<String>()
 
@@ -148,11 +149,6 @@
                 return name
             }
 
-            fun setLogFile(level: LogLevel, filename: String) {
-                log.addFilePrinter(level, filename)
-                log.i("$level log file: $filename")
-            }
-
             while (true) {
                 val arg = ai.nextArgOptional()
                 if (arg == null) {
@@ -161,33 +157,23 @@
 
                 // Define some shorthands...
                 fun nextArg(): String = ai.nextArgRequired(arg)
-                fun SetOnce<String>.setNextStringArg(): String = nextArg().also { this.set(it) }
-                fun SetOnce<String?>.setNextStringArg(): String = nextArg().also { this.set(it) }
                 fun MutableSet<String>.addUniqueAnnotationArg(): String =
                         nextArg().also { this += ensureUniqueAnnotation(it) }
-                fun SetOnce<Int>.setNextIntArg(): String = nextArg().also {
-                    try {
-                        this.set(it.toInt())
-                    } catch (e: NumberFormatException) {
-                        throw ArgumentsException("Invalid integer for $arg: $it")
-                    }
-                }
 
+                if (log.maybeHandleCommandLineArg(arg) { nextArg() }) {
+                    continue
+                }
                 try {
                     when (arg) {
                         // TODO: Write help
                         "-h", "--help" -> TODO("Help is not implemented yet")
 
-                        "-v", "--verbose" -> log.setConsoleLogLevel(LogLevel.Verbose)
-                        "-d", "--debug" -> log.setConsoleLogLevel(LogLevel.Debug)
-                        "-q", "--quiet" -> log.setConsoleLogLevel(LogLevel.None)
-
-                        "--in-jar" -> ret.inJar.setNextStringArg().ensureFileExists()
-                        "--out-stub-jar" -> ret.outStubJar.setNextStringArg()
-                        "--out-impl-jar" -> ret.outImplJar.setNextStringArg()
+                        "--in-jar" -> ret.inJar.set(nextArg()).ensureFileExists()
+                        "--out-stub-jar" -> ret.outStubJar.set(nextArg())
+                        "--out-impl-jar" -> ret.outImplJar.set(nextArg())
 
                         "--policy-override-file" ->
-                            ret.policyOverrideFile.setNextStringArg().ensureFileExists()
+                            ret.policyOverrideFile.set(nextArg())!!.ensureFileExists()
 
                         "--clean-up-on-error" -> ret.cleanUpOnError.set(true)
                         "--no-clean-up-on-error" -> ret.cleanUpOnError.set(false)
@@ -231,19 +217,19 @@
                             ret.packageRedirects += parsePackageRedirect(nextArg())
 
                         "--annotation-allowed-classes-file" ->
-                            ret.annotationAllowedClassesFile.setNextStringArg()
+                            ret.annotationAllowedClassesFile.set(nextArg())
 
                         "--default-class-load-hook" ->
-                            ret.defaultClassLoadHook.setNextStringArg()
+                            ret.defaultClassLoadHook.set(nextArg())
 
                         "--default-method-call-hook" ->
-                            ret.defaultMethodCallHook.setNextStringArg()
+                            ret.defaultMethodCallHook.set(nextArg())
 
                         "--intersect-stub-jar" ->
                             ret.intersectStubJars += nextArg().ensureFileExists()
 
                         "--gen-keep-all-file" ->
-                            ret.inputJarAsKeepAllFile.setNextStringArg()
+                            ret.inputJarAsKeepAllFile.set(nextArg())
 
                         // Following options are for debugging.
                         "--enable-class-checker" -> ret.enableClassChecker.set(true)
@@ -261,16 +247,21 @@
                         "--no-non-stub-method-check" ->
                             ret.enableNonStubMethodCallDetection.set(false)
 
-                        "--gen-input-dump-file" -> ret.inputJarDumpFile.setNextStringArg()
+                        "--gen-input-dump-file" -> ret.inputJarDumpFile.set(nextArg())
 
-                        "--verbose-log" -> setLogFile(LogLevel.Verbose, nextArg())
-                        "--debug-log" -> setLogFile(LogLevel.Debug, nextArg())
+                        "--stats-file" -> ret.statsFile.set(nextArg())
+                        "--supported-api-list-file" -> ret.apiListFile.set(nextArg())
 
-                        "--stats-file" -> ret.statsFile.setNextStringArg()
-                        "--supported-api-list-file" -> ret.apiListFile.setNextStringArg()
-
-                        "--num-shards" -> ret.numShards.setNextIntArg()
-                        "--shard-index" -> ret.shard.setNextIntArg()
+                        "--num-shards" -> ret.numShards.set(nextArg()).also {
+                            if (it < 1) {
+                                throw ArgumentsException("$arg must be positive integer")
+                            }
+                        }
+                        "--shard-index" -> ret.shard.set(nextArg()).also {
+                            if (it < 0) {
+                                throw ArgumentsException("$arg must be positive integer or zero")
+                            }
+                        }
 
                         else -> throw ArgumentsException("Unknown option: $arg")
                     }
@@ -286,6 +277,15 @@
                 log.w("Neither --out-stub-jar nor --out-impl-jar is set." +
                         " $executableName will not generate jar files.")
             }
+            if (ret.numShards.isSet != ret.shard.isSet) {
+                throw ArgumentsException("--num-shards and --shard-index must be used together")
+            }
+
+            if (ret.numShards.isSet) {
+                if (ret.shard.get >= ret.numShards.get) {
+                    throw ArgumentsException("--shard-index must be smaller than --num-shards")
+                }
+            }
 
             if (ret.enableNonStubMethodCallDetection.get) {
                 log.w("--enable-non-stub-method-check is not fully implemented yet." +
@@ -294,87 +294,6 @@
 
             return ret
         }
-
-        /**
-         * Scan the arguments, and if any of them starts with an `@`, then load from the file
-         * and use its content as arguments.
-         *
-         * In this file, each line is treated as a single argument.
-         *
-         * The file can contain '#' as comments.
-         */
-        private fun expandAtFiles(args: Array<String>): List<String> {
-            val ret = mutableListOf<String>()
-
-            args.forEach { arg ->
-                if (!arg.startsWith('@')) {
-                    ret += arg
-                    return@forEach
-                }
-                // Read from the file, and add each line to the result.
-                val filename = arg.substring(1).ensureFileExists()
-
-                log.v("Expanding options file $filename")
-
-                BufferedReader(FileReader(filename)).use { reader ->
-                    while (true) {
-                        var line = reader.readLine()
-                        if (line == null) {
-                            break // EOF
-                        }
-
-                        line = normalizeTextLine(line)
-                        if (line.isNotEmpty()) {
-                            ret += line
-                        }
-                    }
-                }
-            }
-            return ret
-        }
-    }
-
-    open class ArgumentsException(message: String?) : Exception(message), UserErrorException
-
-    /** Thrown when the same annotation is used with different annotation arguments. */
-    class DuplicateAnnotationException(annotationName: String?) :
-            ArgumentsException("Duplicate annotation specified: '$annotationName'")
-
-    /** Thrown when an input file does not exist. */
-    class InputFileNotFoundException(filename: String) :
-            ArgumentsException("File '$filename' not found")
-
-    private class ArgIterator(
-            private val args: List<String>,
-            private var currentIndex: Int = -1
-    ) {
-        val current: String
-            get() = args.get(currentIndex)
-
-        /**
-         * Get the next argument, or [null] if there's no more arguments.
-         */
-        fun nextArgOptional(): String? {
-            if ((currentIndex + 1) >= args.size) {
-                return null
-            }
-            return args.get(++currentIndex)
-        }
-
-        /**
-         * Get the next argument, or throw if
-         */
-        fun nextArgRequired(argName: String): String {
-            nextArgOptional().let {
-                if (it == null) {
-                    throw ArgumentsException("Missing parameter for option $argName")
-                }
-                if (it.isEmpty()) {
-                    throw ArgumentsException("Parameter can't be empty for option $argName")
-                }
-                return it
-            }
-        }
     }
 
     override fun toString(): String {
@@ -415,3 +334,80 @@
             """.trimIndent()
     }
 }
+
+class ArgIterator(
+    private val args: List<String>,
+    private var currentIndex: Int = -1
+) {
+    val current: String
+        get() = args.get(currentIndex)
+
+    /**
+     * Get the next argument, or [null] if there's no more arguments.
+     */
+    fun nextArgOptional(): String? {
+        if ((currentIndex + 1) >= args.size) {
+            return null
+        }
+        return args.get(++currentIndex)
+    }
+
+    /**
+     * Get the next argument, or throw if
+     */
+    fun nextArgRequired(argName: String): String {
+        nextArgOptional().let {
+            if (it == null) {
+                throw ArgumentsException("Missing parameter for option $argName")
+            }
+            if (it.isEmpty()) {
+                throw ArgumentsException("Parameter can't be empty for option $argName")
+            }
+            return it
+        }
+    }
+
+    companion object {
+        fun withAtFiles(args: Array<String>): ArgIterator {
+            return ArgIterator(expandAtFiles(args))
+        }
+    }
+}
+
+/**
+ * Scan the arguments, and if any of them starts with an `@`, then load from the file
+ * and use its content as arguments.
+ *
+ * In this file, each line is treated as a single argument.
+ *
+ * The file can contain '#' as comments.
+ */
+private fun expandAtFiles(args: Array<String>): List<String> {
+    val ret = mutableListOf<String>()
+
+    args.forEach { arg ->
+        if (!arg.startsWith('@')) {
+            ret += arg
+            return@forEach
+        }
+        // Read from the file, and add each line to the result.
+        val filename = arg.substring(1).ensureFileExists()
+
+        log.v("Expanding options file $filename")
+
+        BufferedReader(FileReader(filename)).use { reader ->
+            while (true) {
+                var line = reader.readLine()
+                if (line == null) {
+                    break // EOF
+                }
+
+                line = normalizeTextLine(line)
+                if (line.isNotEmpty()) {
+                    ret += line
+                }
+            }
+        }
+    }
+    return ret
+}
diff --git a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/asm/AsmUtils.kt b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/asm/AsmUtils.kt
index f219dac..6cf2143 100644
--- a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/asm/AsmUtils.kt
+++ b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/asm/AsmUtils.kt
@@ -58,7 +58,24 @@
     return null
 }
 
-fun findAnnotationValueAsString(an: AnnotationNode, propertyName: String): String? {
+fun ClassNode.findAnyAnnotation(set: Set<String>): AnnotationNode? {
+    return findAnyAnnotation(set, this.visibleAnnotations, this.invisibleAnnotations)
+}
+
+fun MethodNode.findAnyAnnotation(set: Set<String>): AnnotationNode? {
+    return findAnyAnnotation(set, this.visibleAnnotations, this.invisibleAnnotations)
+}
+
+fun FieldNode.findAnyAnnotation(set: Set<String>): AnnotationNode? {
+    return findAnyAnnotation(set, this.visibleAnnotations, this.invisibleAnnotations)
+}
+
+fun <T> findAnnotationValueAsObject(
+    an: AnnotationNode,
+    propertyName: String,
+    expectedTypeHumanReadableName: String,
+    converter: (Any?) -> T?,
+): T? {
     for (i in 0..(an.values?.size ?: 0) - 2 step 2) {
         val name = an.values[i]
 
@@ -66,16 +83,30 @@
             continue
         }
         val value = an.values[i + 1]
-        if (value is String) {
-            return value
+        if (value == null) {
+            return null
         }
-        throw ClassParseException(
-                "The type of '$name' in annotation \"${an.desc}\" must be String" +
-                        ", but is ${value?.javaClass?.canonicalName}")
+
+        try {
+            return converter(value)
+        } catch (e: ClassCastException) {
+            throw ClassParseException(
+                "The type of '$propertyName' in annotation @${an.desc} must be " +
+                        "$expectedTypeHumanReadableName, but is ${value?.javaClass?.canonicalName}")
+        }
     }
     return null
 }
 
+fun findAnnotationValueAsString(an: AnnotationNode, propertyName: String): String? {
+    return findAnnotationValueAsObject(an, propertyName, "String", {it as String})
+}
+
+fun findAnnotationValueAsType(an: AnnotationNode, propertyName: String): Type? {
+    return findAnnotationValueAsObject(an, propertyName, "Class", {it as Type})
+}
+
+
 val periodOrSlash = charArrayOf('.', '/')
 
 fun getPackageNameFromFullClassName(fullClassName: String): String {
@@ -125,6 +156,24 @@
     return Pair(name.substring(0, pos), name.substring(pos + 1))
 }
 
+fun String.startsWithAny(vararg prefixes: String): Boolean {
+    prefixes.forEach {
+        if (this.startsWith(it)) {
+            return true
+        }
+    }
+    return false
+}
+
+fun String.endsWithAny(vararg suffixes: String): Boolean {
+    suffixes.forEach {
+        if (this.endsWith(it)) {
+            return true
+        }
+    }
+    return false
+}
+
 fun String.toJvmClassName(): String {
     return this.replace('.', '/')
 }
@@ -137,6 +186,14 @@
     return this.replace('/', '.')
 }
 
+fun zipEntryNameToClassName(entryFilename: String): String? {
+    val suffix = ".class"
+    if (!entryFilename.endsWith(suffix)) {
+        return null
+    }
+    return entryFilename.substring(0, entryFilename.length - suffix.length)
+}
+
 private val numericalInnerClassName = """.*\$\d+$""".toRegex()
 
 fun isAnonymousInnerClass(cn: ClassNode): Boolean {
@@ -278,6 +335,14 @@
     return (this.access and Opcodes.ACC_STATIC) != 0
 }
 
+fun MethodNode.isPublic(): Boolean {
+    return (this.access and Opcodes.ACC_PUBLIC) != 0
+}
+
+fun MethodNode.isSpecial(): Boolean {
+    return CTOR_NAME == this.name || CLASS_INITIALIZER_NAME == this.name
+}
+
 fun FieldNode.isEnum(): Boolean {
     return (this.access and Opcodes.ACC_ENUM) != 0
 }
diff --git a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/asm/ClassNodes.kt b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/asm/ClassNodes.kt
index 2607df6..e2647eb 100644
--- a/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/asm/ClassNodes.kt
+++ b/tools/hoststubgen/hoststubgen/src/com/android/hoststubgen/asm/ClassNodes.kt
@@ -27,6 +27,11 @@
 import java.io.BufferedInputStream
 import java.io.PrintWriter
 import java.util.Arrays
+import java.util.concurrent.Executors
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.atomic.AtomicReference
+import java.util.function.Consumer
+import java.util.zip.ZipEntry
 import java.util.zip.ZipFile
 
 /**
@@ -183,10 +188,43 @@
         /**
          * Load all the classes, without code.
          */
-        fun loadClassStructures(inJar: String): ClassNodes {
-            log.iTime("Reading class structure from $inJar") {
-                val allClasses = ClassNodes()
+        fun loadClassStructures(
+            inJar: String,
+            timeCollector: Consumer<Double>? = null,
+        ): ClassNodes {
+            val allClasses = ClassNodes()
 
+            // Load classes in parallel.
+            val executor = Executors.newFixedThreadPool(4)
+
+            // First exception defected.
+            val exception = AtomicReference<Throwable>()
+
+            // Called on a BG thread. Read a single jar entry and add it to [allClasses].
+            fun parseClass(inZip: ZipFile, entry: ZipEntry) {
+                try {
+                    inZip.getInputStream(entry).use { ins ->
+                        val cr = ClassReader(BufferedInputStream(ins))
+                        val cn = ClassNode()
+                        cr.accept(
+                            cn, ClassReader.SKIP_CODE
+                                    or ClassReader.SKIP_DEBUG
+                                    or ClassReader.SKIP_FRAMES
+                        )
+                        synchronized(allClasses) {
+                            if (!allClasses.addClass(cn)) {
+                                log.w("Duplicate class found: ${cn.name}")
+                            }
+                        }
+                    }
+                } catch (e: Throwable) {
+                    log.e("Failed to load class: $e")
+                    exception.compareAndSet(null, e)
+                }
+            }
+
+            // Actually open the jar and read it on worker threads.
+            val time = log.iTime("Reading class structure from $inJar") {
                 log.withIndent {
                     ZipFile(inJar).use { inZip ->
                         val inEntries = inZip.entries()
@@ -194,40 +232,42 @@
                         while (inEntries.hasMoreElements()) {
                             val entry = inEntries.nextElement()
 
-                            BufferedInputStream(inZip.getInputStream(entry)).use { bis ->
-                                if (entry.name.endsWith(".class")) {
-                                    val cr = ClassReader(bis)
-                                    val cn = ClassNode()
-                                    cr.accept(
-                                        cn, ClassReader.SKIP_CODE
-                                                or ClassReader.SKIP_DEBUG
-                                                or ClassReader.SKIP_FRAMES
-                                    )
-                                    if (!allClasses.addClass(cn)) {
-                                        log.w("Duplicate class found: ${cn.name}")
-                                    }
-                                } else if (entry.name.endsWith(".dex")) {
-                                    // Seems like it's an ART jar file. We can't process it.
-                                    // It's a fatal error.
-                                    throw InvalidJarFileException(
-                                        "$inJar is not a desktop jar file."
-                                        + " It contains a *.dex file."
-                                    )
-                                } else {
-                                    // Unknown file type. Skip.
-                                    while (bis.available() > 0) {
-                                        bis.skip((1024 * 1024).toLong())
-                                    }
+                            if (entry.name.endsWith(".class")) {
+                                executor.submit {
+                                    parseClass(inZip, entry)
                                 }
+                            } else if (entry.name.endsWith(".dex")) {
+                                // Seems like it's an ART jar file. We can't process it.
+                                // It's a fatal error.
+                                throw InvalidJarFileException(
+                                    "$inJar is not a desktop jar file."
+                                            + " It contains a *.dex file."
+                                )
+                            } else {
+                                // Unknown file type. Skip.
                             }
                         }
+                        // Wait for all the work to complete. (must do it before closing the zip)
+                        log.i("Waiting for all loaders to finish...")
+                        executor.shutdown()
+                        executor.awaitTermination(5, TimeUnit.MINUTES)
+                        log.i("All loaders to finished.")
                     }
                 }
+
+                // If any exception is detected, throw it.
+                exception.get()?.let {
+                    throw it
+                }
+
                 if (allClasses.size == 0) {
                     log.w("$inJar contains no *.class files.")
+                } else {
+                    log.i("Loaded ${allClasses.size} classes from $inJar.")
                 }
-                return allClasses
             }
+            timeCollector?.accept(time)
+            return allClasses
         }
     }
 }
\ No newline at end of file