### Eclipse Workspace Patch 1.0
#P org.eclipse.jdt.launching
Index: launching/org/eclipse/jdt/launching/JavaRuntime.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.launching/launching/org/eclipse/jdt/launching/JavaRuntime.java,v
retrieving revision 1.218
diff -u -r1.218 JavaRuntime.java
--- launching/org/eclipse/jdt/launching/JavaRuntime.java	27 Jul 2010 18:32:16 -0000	1.218
+++ launching/org/eclipse/jdt/launching/JavaRuntime.java	5 Nov 2010 10:39:54 -0000
@@ -18,9 +18,12 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.StringReader;
+import java.lang.ref.Reference;
+import java.lang.ref.SoftReference;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Hashtable;
@@ -31,18 +34,10 @@
 
 import javax.xml.parsers.DocumentBuilder;
 
-import com.ibm.icu.text.MessageFormat;
-
-import org.xml.sax.InputSource;
-import org.xml.sax.SAXException;
-
-import org.w3c.dom.Element;
-import org.w3c.dom.Node;
-import org.w3c.dom.NodeList;
-
-import org.eclipse.core.variables.IStringVariableManager;
-import org.eclipse.core.variables.VariablesPlugin;
-
+import org.eclipse.core.resources.IProject;
+import org.eclipse.core.resources.IResource;
+import org.eclipse.core.resources.IWorkspaceRoot;
+import org.eclipse.core.resources.ResourcesPlugin;
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IConfigurationElement;
 import org.eclipse.core.runtime.IExtensionPoint;
@@ -56,22 +51,16 @@
 import org.eclipse.core.runtime.Preferences;
 import org.eclipse.core.runtime.Status;
 import org.eclipse.core.runtime.preferences.BundleDefaultsScope;
-
-import org.eclipse.core.resources.IProject;
-import org.eclipse.core.resources.IResource;
-import org.eclipse.core.resources.IWorkspaceRoot;
-import org.eclipse.core.resources.ResourcesPlugin;
-
+import org.eclipse.core.variables.IStringVariableManager;
+import org.eclipse.core.variables.VariablesPlugin;
 import org.eclipse.debug.core.ILaunchConfiguration;
 import org.eclipse.debug.core.sourcelookup.ISourceContainer;
-
 import org.eclipse.jdt.core.IClasspathAttribute;
 import org.eclipse.jdt.core.IClasspathContainer;
 import org.eclipse.jdt.core.IClasspathEntry;
 import org.eclipse.jdt.core.IJavaModel;
 import org.eclipse.jdt.core.IJavaProject;
 import org.eclipse.jdt.core.JavaCore;
-
 import org.eclipse.jdt.internal.launching.CompositeId;
 import org.eclipse.jdt.internal.launching.DefaultEntryResolver;
 import org.eclipse.jdt.internal.launching.DefaultProjectClasspathEntry;
@@ -90,10 +79,16 @@
 import org.eclipse.jdt.internal.launching.VMListener;
 import org.eclipse.jdt.internal.launching.VariableClasspathEntry;
 import org.eclipse.jdt.internal.launching.environments.EnvironmentsManager;
-
 import org.eclipse.jdt.launching.environments.ExecutionEnvironmentDescription;
 import org.eclipse.jdt.launching.environments.IExecutionEnvironment;
 import org.eclipse.jdt.launching.environments.IExecutionEnvironmentsManager;
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+import org.w3c.dom.NodeList;
+import org.xml.sax.InputSource;
+import org.xml.sax.SAXException;
+
+import com.ibm.icu.text.MessageFormat;
 
 /**
  * The central access point for launching support. This class manages
@@ -329,6 +324,11 @@
      */
     private static Set fgContributedVMs = new HashSet();
     
+    /**
+     * Cache of VM install location to prevent needless I/O.
+     */
+    private static Map/*<IVMInstall, Reference<ILocation[]>*/ fLibraryLocationCache = Collections.synchronizedMap(new HashMap()); 
+
 	/**
 	 * This class contains only static methods, and is not intended
 	 * to be instantiated.
@@ -1632,6 +1632,12 @@
 	 * @since 2.0
 	 */
 	public static LibraryLocation[] getLibraryLocations(IVMInstall vm)  {
+		Reference/*<ILocation[]>*/ ref = (Reference)fLibraryLocationCache.get(vm);
+		if (ref != null) {
+			LibraryLocation[] locations = (LibraryLocation[])ref.get();
+			if (locations != null)
+				return locations;
+		}
 		IPath[] libraryPaths;
 		IPath[] sourcePaths;
 		IPath[] sourceRootPaths;
@@ -1683,9 +1689,10 @@
 		for (int i = 0; i < sourcePaths.length; i++) {
 			locations[i] = new LibraryLocation(libraryPaths[i], sourcePaths[i], sourceRootPaths[i], javadocLocations[i]);
 		}
+		fLibraryLocationCache.put(vm, new SoftReference(locations));
 		return locations;
 	}
-	
+
 	/**
 	 * Detect the VM that Eclipse is running on.
 	 *