diff --git a/ui/build/java.go b/ui/build/java.go
new file mode 100644
index 0000000..473af01
--- /dev/null
+++ b/ui/build/java.go
@@ -0,0 +1,163 @@
+// Copyright 2017 Google Inc. All rights reserved.
+//
+// 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 build
+
+import (
+	"regexp"
+	"runtime"
+	"strings"
+	"sync"
+)
+
+const incompatibleJavacStr = "google"
+
+var javaVersionInfo = struct {
+	once      sync.Once
+	startOnce sync.Once
+
+	java_version_output  string
+	javac_version_output string
+}{}
+
+func getJavaVersions(ctx Context, config Config) {
+	javaVersionInfo.startOnce.Do(func() {
+		go func() {
+			if ctx.Tracer != nil {
+				thread := ctx.Tracer.NewThread("java_version")
+				ctx.Tracer.Begin("get version", thread)
+				defer ctx.Tracer.End(thread)
+			}
+
+			getJavaVersionsImpl(ctx, config)
+		}()
+	})
+}
+
+func getJavaVersionsImpl(ctx Context, config Config) {
+	javaVersionInfo.once.Do(func() {
+		cmd := Command(ctx, config, "java", "java", "-version")
+		cmd.Environment.Unset("_JAVA_OPTIONS")
+		javaVersionInfo.java_version_output = string(cmd.CombinedOutputOrFatal())
+
+		cmd = Command(ctx, config, "javac", "javac", "-version")
+		cmd.Environment.Unset("_JAVA_OPTIONS")
+		javaVersionInfo.javac_version_output = string(cmd.CombinedOutputOrFatal())
+	})
+}
+
+func checkJavaVersion(ctx Context, config Config) {
+	ctx.BeginTrace("java_version_check")
+	defer ctx.EndTrace()
+
+	getJavaVersionsImpl(ctx, config)
+
+	var required_java_version string
+	var java_version_regexp *regexp.Regexp
+	var javac_version_regexp *regexp.Regexp
+
+	oj9_env, _ := config.Environment().Get("EXPERIMENTAL_USE_OPENJDK9")
+	experimental_use_openjdk9 := oj9_env != ""
+
+	if experimental_use_openjdk9 {
+		required_java_version = "9"
+		java_version_regexp = regexp.MustCompile(`^java .* "9.*"`)
+		javac_version_regexp = regexp.MustCompile(`^javac 9`)
+	} else {
+		required_java_version = "1.8"
+		java_version_regexp = regexp.MustCompile(`[ "]1\.8[\. "$]`)
+		javac_version_regexp = java_version_regexp
+	}
+
+	java_version := javaVersionInfo.java_version_output
+	javac_version := javaVersionInfo.javac_version_output
+
+	found := false
+	for _, l := range strings.Split(java_version, "\n") {
+		if java_version_regexp.MatchString(l) {
+			java_version = l
+			found = true
+			break
+		}
+	}
+	if !found {
+		ctx.Println("***************************************************************")
+		ctx.Println("You are attempting to build with the incorrect version of java.")
+		ctx.Println()
+		ctx.Println("Your version is:", java_version)
+		ctx.Println("The required version is:", required_java_version+".x")
+		ctx.Println()
+		ctx.Println("Please follow the machine setup instructions at:")
+		ctx.Println("    https://source.android.com/source/initializing.html")
+		ctx.Println("***************************************************************")
+		ctx.Fatalln("stop")
+	}
+
+	if runtime.GOOS == "linux" {
+		// Early access builds of OpenJDK 9 do not contain the string "openjdk" in the
+		// version name. TODO(tobiast): Reconsider once the OpenJDK 9 toolchain is stable.
+		// http://b/62123342
+		if !strings.Contains(java_version, "openjdk") && !experimental_use_openjdk9 {
+			ctx.Println("*******************************************************")
+			ctx.Println("You are attempting to build with an unsupported JDK.")
+			ctx.Println()
+			ctx.Println("Only an OpenJDK based JDK is supported.")
+			ctx.Println()
+			ctx.Println("Please follow the machine setup instructions at:")
+			ctx.Println("    https://source.android.com/source/initializing.html")
+			ctx.Println("*******************************************************")
+			ctx.Fatalln("stop")
+		}
+	} else { // darwin
+		if strings.Contains(java_version, "openjdk") {
+			ctx.Println("*******************************************************")
+			ctx.Println("You are attempting to build with an unsupported JDK.")
+			ctx.Println()
+			ctx.Println("You use OpenJDK, but only Sun/Oracle JDK is supported.")
+			ctx.Println()
+			ctx.Println("Please follow the machine setup instructions at:")
+			ctx.Println("    https://source.android.com/source/initializing.html")
+			ctx.Println("*******************************************************")
+			ctx.Fatalln("stop")
+		}
+	}
+
+	incompatible_javac := strings.Contains(javac_version, incompatibleJavacStr)
+
+	found = false
+	for _, l := range strings.Split(javac_version, "\n") {
+		if javac_version_regexp.MatchString(l) {
+			javac_version = l
+			found = true
+			break
+		}
+	}
+	if !found || incompatible_javac {
+		ctx.Println("****************************************************************")
+		ctx.Println("You are attempting to build with the incorrect version of javac.")
+		ctx.Println()
+		ctx.Println("Your version is:", javac_version)
+		if incompatible_javac {
+			ctx.Println("The '" + incompatibleJavacStr + "' version is not supported for Android platform builds.")
+			ctx.Println("Use a publically available JDK and make sure you have run envsetup.sh / lunch.")
+		} else {
+			ctx.Println("The required version is:", required_java_version)
+		}
+		ctx.Println()
+		ctx.Println("Please follow the machine setup instructions at:")
+		ctx.Println("    https://source.android.com/source/initializing.html")
+		ctx.Println("****************************************************************")
+		ctx.Fatalln("stop")
+	}
+}