diff --git a/java/classpath_element.go b/java/classpath_element.go
new file mode 100644
index 0000000..753e7f8
--- /dev/null
+++ b/java/classpath_element.go
@@ -0,0 +1,229 @@
+/*
+ * Copyright (C) 2021 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 java
+
+import (
+	"fmt"
+	"strings"
+
+	"android/soong/android"
+	"github.com/google/blueprint"
+)
+
+// Supports constructing a list of ClasspathElement from a set of fragments and modules.
+
+// ClasspathElement represents a component that contributes to a classpath. That can be
+// either a java module or a classpath fragment module.
+type ClasspathElement interface {
+	Module() android.Module
+	String() string
+}
+
+type ClasspathElements []ClasspathElement
+
+// ClasspathFragmentElement is a ClasspathElement that encapsulates a classpath fragment module.
+type ClasspathFragmentElement struct {
+	Fragment android.Module
+	Contents []android.Module
+}
+
+func (b *ClasspathFragmentElement) Module() android.Module {
+	return b.Fragment
+}
+
+func (b *ClasspathFragmentElement) String() string {
+	contents := []string{}
+	for _, module := range b.Contents {
+		contents = append(contents, module.String())
+	}
+	return fmt.Sprintf("fragment(%s, %s)", b.Fragment, strings.Join(contents, ", "))
+}
+
+var _ ClasspathElement = (*ClasspathFragmentElement)(nil)
+
+// ClasspathLibraryElement is a ClasspathElement that encapsulates a java library.
+type ClasspathLibraryElement struct {
+	Library android.Module
+}
+
+func (b *ClasspathLibraryElement) Module() android.Module {
+	return b.Library
+}
+
+func (b *ClasspathLibraryElement) String() string {
+	return fmt.Sprintf("library{%s}", b.Library)
+}
+
+var _ ClasspathElement = (*ClasspathLibraryElement)(nil)
+
+// ClasspathElementContext defines the context methods needed by CreateClasspathElements
+type ClasspathElementContext interface {
+	OtherModuleHasProvider(m blueprint.Module, provider blueprint.ProviderKey) bool
+	OtherModuleProvider(m blueprint.Module, provider blueprint.ProviderKey) interface{}
+	ModuleErrorf(fmt string, args ...interface{})
+}
+
+// CreateClasspathElements creates a list of ClasspathElement objects from a list of libraries and
+// a list of fragments.
+//
+// The libraries parameter contains the set of libraries from which the classpath is constructed.
+// The fragments parameter contains the classpath fragment modules whose contents are libraries that
+// are part of the classpath. Each library in the libraries parameter may be part of a fragment. The
+// determination as to which libraries belong to fragments and which do not is based on the apex to
+// which they belong, if any.
+//
+// Every fragment in the fragments list must be part of one or more apexes and each apex is assumed
+// to contain only a single fragment from the fragments list. A library in the libraries parameter
+// that is part of an apex must be provided by a classpath fragment in the corresponding apex.
+//
+// This will return a ClasspathElements list that contains a ClasspathElement for each standalone
+// library and each fragment. The order of the elements in the list is such that if the list was
+// flattened into a list of library modules that it would result in the same list or modules as the
+// input libraries. Flattening the list can be done by replacing each ClasspathFragmentElement in
+// the list with its Contents field.
+//
+// Requirements/Assumptions:
+// * A fragment can be associated with more than one apex but each apex must only be associated with
+//   a single fragment from the fragments list.
+// * All of a fragment's contents must appear as a contiguous block in the same order in the
+//   libraries list.
+// * Each library must only appear in a single fragment.
+//
+// The apex is used to identify which libraries belong to which fragment. First a mapping is created
+// from apex to fragment. Then the libraries are iterated over and any library in an apex is
+// associated with an element for the fragment to which it belongs. Otherwise, the libraries are
+// standalone and have their own element.
+//
+// e.g. Given the following input:
+//     libraries: com.android.art:core-oj, com.android.art:core-libart, framework, ext
+//     fragments: com.android.art:art-bootclasspath-fragment
+//
+// Then this will return:
+//     ClasspathFragmentElement(art-bootclasspath-fragment, [core-oj, core-libart]),
+//     ClasspathLibraryElement(framework),
+//     ClasspathLibraryElement(ext),
+func CreateClasspathElements(ctx ClasspathElementContext, libraries []android.Module, fragments []android.Module) ClasspathElements {
+	// Create a map from apex name to the fragment module. This makes it easy to find the fragment
+	// associated with a particular apex.
+	apexToFragment := map[string]android.Module{}
+	for _, fragment := range fragments {
+		if !ctx.OtherModuleHasProvider(fragment, android.ApexInfoProvider) {
+			ctx.ModuleErrorf("fragment %s is not part of an apex", fragment)
+			continue
+		}
+
+		apexInfo := ctx.OtherModuleProvider(fragment, android.ApexInfoProvider).(android.ApexInfo)
+		for _, apex := range apexInfo.InApexVariants {
+			if existing, ok := apexToFragment[apex]; ok {
+				ctx.ModuleErrorf("apex %s has multiple fragments, %s and %s", apex, fragment, existing)
+				continue
+			}
+			apexToFragment[apex] = fragment
+		}
+	}
+
+	fragmentToElement := map[android.Module]*ClasspathFragmentElement{}
+	elements := []ClasspathElement{}
+	var currentElement ClasspathElement
+
+skipLibrary:
+	// Iterate over the libraries to construct the ClasspathElements list.
+	for _, library := range libraries {
+		var element ClasspathElement
+		if ctx.OtherModuleHasProvider(library, android.ApexInfoProvider) {
+			apexInfo := ctx.OtherModuleProvider(library, android.ApexInfoProvider).(android.ApexInfo)
+
+			var fragment android.Module
+
+			// Make sure that the library is in only one fragment of the classpath.
+			for _, apex := range apexInfo.InApexVariants {
+				if f, ok := apexToFragment[apex]; ok {
+					if fragment == nil {
+						// This is the first fragment so just save it away.
+						fragment = f
+					} else if f != fragment {
+						// This apex variant of the library is in a different fragment.
+						ctx.ModuleErrorf("library %s is in two separate fragments, %s and %s", library, fragment, f)
+						// Skip over this library entirely as otherwise the resulting classpath elements would
+						// be invalid.
+						continue skipLibrary
+					}
+				} else {
+					// There is no fragment associated with the library's apex.
+				}
+			}
+
+			if fragment == nil {
+				ctx.ModuleErrorf("library %s is from apexes %s which have no corresponding fragment in %s",
+					library, apexInfo.InApexVariants, fragments)
+				// Skip over this library entirely as otherwise the resulting classpath elements would
+				// be invalid.
+				continue skipLibrary
+			} else if existingFragmentElement, ok := fragmentToElement[fragment]; ok {
+				// This library is in a fragment element that has already been added.
+
+				// If the existing fragment element is still the current element then this library is
+				// contiguous with other libraries in that fragment so there is nothing more to do.
+				// Otherwise this library is not contiguous with other libraries in the same fragment which
+				// is an error.
+				if existingFragmentElement != currentElement {
+					separator := ""
+					if fragmentElement, ok := currentElement.(*ClasspathFragmentElement); ok {
+						separator = fmt.Sprintf("libraries from fragment %s like %s", fragmentElement.Fragment, fragmentElement.Contents[0])
+					} else {
+						libraryElement := currentElement.(*ClasspathLibraryElement)
+						separator = fmt.Sprintf("library %s", libraryElement.Library)
+					}
+
+					// Get the library that precedes this library in the fragment. That is the last library as
+					// this library has not yet been added.
+					precedingLibraryInFragment := existingFragmentElement.Contents[len(existingFragmentElement.Contents)-1]
+					ctx.ModuleErrorf("libraries from the same fragment must be contiguous, however %s and %s from fragment %s are separated by %s",
+						precedingLibraryInFragment, library, fragment, separator)
+				}
+
+				// Add this library to the fragment element's contents.
+				existingFragmentElement.Contents = append(existingFragmentElement.Contents, library)
+			} else {
+				// This is the first library in this fragment so add a new element for the fragment,
+				// including the library.
+				fragmentElement := &ClasspathFragmentElement{
+					Fragment: fragment,
+					Contents: []android.Module{library},
+				}
+
+				// Store it away so we can detect when attempting to create another element for the same
+				// fragment.
+				fragmentToElement[fragment] = fragmentElement
+				element = fragmentElement
+			}
+		} else {
+			// The library is from the platform so just add an element for it.
+			element = &ClasspathLibraryElement{Library: library}
+		}
+
+		// If no element was created then it means that the library has been added to an existing
+		// fragment element so the list of elements and current element are unaffected.
+		if element != nil {
+			// Add the element to the list and make it the current element for the next iteration.
+			elements = append(elements, element)
+			currentElement = element
+		}
+	}
+
+	return elements
+}