### Eclipse Workspace Patch 1.0
#P org.eclipse.jdt.core.tests.model
Index: src/org/eclipse/jdt/core/tests/model/OptionTests.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core.tests.model/src/org/eclipse/jdt/core/tests/model/OptionTests.java,v
retrieving revision 1.26
diff -u -r1.26 OptionTests.java
--- src/org/eclipse/jdt/core/tests/model/OptionTests.java	27 Jun 2008 16:02:40 -0000	1.26
+++ src/org/eclipse/jdt/core/tests/model/OptionTests.java	21 Jul 2009 20:26:08 -0000
@@ -14,6 +14,8 @@
 import java.util.Map;
 
 import junit.framework.Test;
+
+import org.eclipse.core.resources.ResourcesPlugin;
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.Path;
 import org.eclipse.core.runtime.preferences.DefaultScope;
@@ -522,7 +524,15 @@
 		preferences.remove(JavaModelManager.CP_VARIABLE_PREFERENCES_PREFIX+"TEST");
 	}
 }
-
+// https://bugs.eclipse.org/bugs/show_bug.cgi?id=217443
+public void test13() {
+	Hashtable options = JavaCore.getDefaultOptions();
+	String immutableValue = (String) options.get(JavaCore.CORE_ENCODING);
+	assertEquals(ResourcesPlugin.getEncoding(), immutableValue);
+	options.put(JavaCore.CORE_ENCODING, immutableValue + "_extra_tail");
+	JavaCore.setOptions(options);
+	assertEquals(immutableValue, JavaCore.getOptions().get(JavaCore.CORE_ENCODING));
+}
 /**
  * Bug 68993: [Preferences] IAE when opening project preferences
  * @see "http://bugs.eclipse.org/bugs/show_bug.cgi?id=68993"
#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 1.435
diff -u -r1.435 JavaModelManager.java
--- model/org/eclipse/jdt/internal/core/JavaModelManager.java	7 May 2009 18:00:56 -0000	1.435
+++ model/org/eclipse/jdt/internal/core/JavaModelManager.java	21 Jul 2009 20:26:09 -0000
@@ -1961,11 +1961,11 @@
 		// set options using preferences service lookup
 		Iterator iterator = this.optionNames.iterator();
 		while (iterator.hasNext()) {
-		    String propertyName = (String) iterator.next();
-		    String propertyValue = service.get(propertyName, null, this.preferencesLookup);
-		    if (propertyValue != null) {
-			    options.put(propertyName, propertyValue);
-		    }
+			String propertyName = (String) iterator.next();
+			String propertyValue = service.get(propertyName, null, this.preferencesLookup);
+			if (propertyValue != null) {
+				options.put(propertyName, propertyValue);
+			}
 		}
 
 		// get encoding through resource plugin
@@ -4516,6 +4516,7 @@
 	public void setOptions(Hashtable newOptions) {
 
 		try {
+			Hashtable cachedValue = newOptions == null ? null : new Hashtable(newOptions);
 			IEclipsePreferences defaultPreferences = getDefaultPreferences();
 			IEclipsePreferences instancePreferences = getInstancePreferences();
 
@@ -4526,7 +4527,12 @@
 				while (keys.hasMoreElements()){
 					String key = (String)keys.nextElement();
 					if (!this.optionNames.contains(key)) continue; // unrecognized option
-					if (key.equals(JavaCore.CORE_ENCODING)) continue; // skipped, contributed by resource prefs
+					if (key.equals(JavaCore.CORE_ENCODING)) {
+						if (cachedValue != null) {
+							cachedValue.put(key, JavaCore.getEncoding());
+						}
+						continue; // skipped, contributed by resource prefs
+					}
 					String value = (String)newOptions.get(key);
 					String defaultValue = defaultPreferences.get(key, null);
 					if (defaultValue != null && defaultValue.equals(value)) {
@@ -4541,7 +4547,7 @@
 			instancePreferences.flush();
 
 			// update cache
-			this.optionsCache = newOptions==null ? null : new Hashtable(newOptions);
+			this.optionsCache = cachedValue;
 		} catch (BackingStoreException e) {
 			// ignore
 		}