### Eclipse Workspace Patch 1.0
#P org.eclipse.jdt.core
Index: model/org/eclipse/jdt/internal/core/JavaModelManager.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/JavaModelManager.java,v
retrieving revision 1.430
diff -u -r1.430 JavaModelManager.java
--- model/org/eclipse/jdt/internal/core/JavaModelManager.java	20 Mar 2009 09:09:21 -0000	1.430
+++ model/org/eclipse/jdt/internal/core/JavaModelManager.java	17 Apr 2009 16:29:22 -0000
@@ -1151,8 +1151,7 @@
 		protected ClasspathChange addClasspathChange() {
 			// remember old info
 			JavaModelManager manager = JavaModelManager.getJavaModelManager();
-			DeltaProcessor deltaProcessor = manager.deltaState.getDeltaProcessor();
-			ClasspathChange classpathChange = deltaProcessor.addClasspathChange(this.project, this.rawClasspath, this.outputLocation, this.resolvedClasspath);
+			ClasspathChange classpathChange = manager.deltaState.addClasspathChange(this.project, this.rawClasspath, this.outputLocation, this.resolvedClasspath);
 			return classpathChange;
 		}
 
Index: model/org/eclipse/jdt/internal/core/DeltaProcessingState.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/DeltaProcessingState.java,v
retrieving revision 1.52
diff -u -r1.52 DeltaProcessingState.java
--- model/org/eclipse/jdt/internal/core/DeltaProcessingState.java	20 Mar 2009 09:09:21 -0000	1.52
+++ model/org/eclipse/jdt/internal/core/DeltaProcessingState.java	17 Apr 2009 16:29:20 -0000
@@ -87,6 +87,13 @@
 	/* A table from file system absoulte path (String) to timestamp (Long) */
 	public Hashtable externalTimeStamps;
 
+	/*
+	 * Map from IProject to ClasspathChange
+	 * Note these changes need to be kept on the delta processing state to ensure we don't loose them
+	 * (see https://bugs.eclipse.org/bugs/show_bug.cgi?id=271102 Java model corrupt after switching target platform)
+	 */
+	private HashMap classpathChanges = new HashMap();
+
 	/* A table from JavaProject to ClasspathValidation */
 	private HashMap classpathValidations = new HashMap();
 
@@ -171,6 +178,32 @@
 		return deltaProcessor;
 	}
 
+	public synchronized ClasspathChange addClasspathChange(IProject project, IClasspathEntry[] oldRawClasspath, IPath oldOutputLocation, IClasspathEntry[] oldResolvedClasspath) {
+		ClasspathChange change = (ClasspathChange) this.classpathChanges.get(project);
+		if (change == null) {
+			change = new ClasspathChange((JavaProject) JavaModelManager.getJavaModelManager().getJavaModel().getJavaProject(project), oldRawClasspath, oldOutputLocation, oldResolvedClasspath);
+			this.classpathChanges.put(project, change);
+		} else {
+			if (change.oldRawClasspath == null)
+				change.oldRawClasspath = oldRawClasspath;
+			if (change.oldOutputLocation == null)
+				change.oldOutputLocation = oldOutputLocation;
+			if (change.oldResolvedClasspath == null)
+				change.oldResolvedClasspath = oldResolvedClasspath;
+		}
+		return change;
+	}
+	
+	public synchronized ClasspathChange getClasspathChange(IProject project) {
+		return (ClasspathChange) this.classpathChanges.get(project);
+	}
+	
+	public synchronized HashMap removeAllClasspathChanges() {
+		HashMap result = this.classpathChanges;
+		this.classpathChanges = new HashMap(result.size());
+		return result;
+	}
+
 	public synchronized ClasspathValidation addClasspathValidation(JavaProject project) {
 		ClasspathValidation validation = (ClasspathValidation) this.classpathValidations.get(project);
 		if (validation == null) {
Index: model/org/eclipse/jdt/internal/core/DeltaProcessor.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/DeltaProcessor.java,v
retrieving revision 1.333
diff -u -r1.333 DeltaProcessor.java
--- model/org/eclipse/jdt/internal/core/DeltaProcessor.java	7 Mar 2009 00:58:57 -0000	1.333
+++ model/org/eclipse/jdt/internal/core/DeltaProcessor.java	17 Apr 2009 16:29:21 -0000
@@ -252,32 +252,11 @@
 	 */
 	private SourceElementParser sourceElementParserCache;
 
-	/*
-	 * Map from IProject to ClasspathChange
-	 */
-	public HashMap classpathChanges = new HashMap();
-
 	public DeltaProcessor(DeltaProcessingState state, JavaModelManager manager) {
 		this.state = state;
 		this.manager = manager;
 	}
 
-	public ClasspathChange addClasspathChange(IProject project, IClasspathEntry[] oldRawClasspath, IPath oldOutputLocation, IClasspathEntry[] oldResolvedClasspath) {
-		ClasspathChange change = (ClasspathChange) this.classpathChanges.get(project);
-		if (change == null) {
-			change = new ClasspathChange((JavaProject) this.manager.getJavaModel().getJavaProject(project), oldRawClasspath, oldOutputLocation, oldResolvedClasspath);
-			this.classpathChanges.put(project, change);
-		} else {
-			if (change.oldRawClasspath == null)
-				change.oldRawClasspath = oldRawClasspath;
-			if (change.oldOutputLocation == null)
-				change.oldOutputLocation = oldOutputLocation;
-			if (change.oldResolvedClasspath == null)
-				change.oldResolvedClasspath = oldResolvedClasspath;
-		}
-		return change;
-	}
-
 	/*
 	 * Adds the dependents of the given project to the list of the projects
 	 * to update.
@@ -487,12 +466,12 @@
 	}
 
 	private void checkExternalFolderChange(IProject project, JavaProject javaProject) {
-		ClasspathChange change = (ClasspathChange) this.classpathChanges.get(project);
+		ClasspathChange change = this.state.getClasspathChange(project);
 		this.state.addExternalFolderChange(javaProject, change == null ? null : change.oldResolvedClasspath);
 	}
 
 	private void checkProjectReferenceChange(IProject project, JavaProject javaProject) {
-		ClasspathChange change = (ClasspathChange) this.classpathChanges.get(project);
+		ClasspathChange change = this.state.getClasspathChange(project);
 		this.state.addProjectReferenceChange(javaProject, change == null ? null : change.oldResolvedClasspath);
 	}
 
@@ -1927,10 +1906,11 @@
 							}
 
 							// generate classpath change deltas
-							if (this.classpathChanges.size() > 0) {
+							HashMap classpathChanges = this.state.removeAllClasspathChanges();
+							if (classpathChanges.size() > 0) {
 								boolean hasDelta = this.currentDelta != null;
 								JavaElementDelta javaDelta = currentDelta();
-								Iterator changes = this.classpathChanges.values().iterator();
+								Iterator changes = classpathChanges.values().iterator();
 								while (changes.hasNext()) {
 									ClasspathChange change = (ClasspathChange) changes.next();
 									int result = change.generateDelta(javaDelta);
@@ -1955,7 +1935,6 @@
 								if (elementsToRefresh != null) {
 									hasDelta |= createExternalArchiveDelta(elementsToRefresh, null);
 								}
-								this.classpathChanges.clear();
 								if (!hasDelta)
 									this.currentDelta = null;
 							}