Bug 30751 [Viewers] Closing all projects doesnt clear package browser list [browsing]
In the java browsing perspective, if you close all projects, the packages browser still has a list of all the packages from the last opened project.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/StructuredViewer.java
public void setSorter(ViewerSorter sorter) {
	if (this.sorter != sorter) {
		this.sorter = sorter;
		refresh();
	}
}
/**
 * Configures whether this structured viewer uses an internal hash table to
 * speeds up the mapping between elements and SWT items.
 * This must be called before the viewer is given an input (via <code>setInput</code>).
 *
 * @param enable <code>true</code> to enable hash lookup, and <code>false</code> to disable it
 */
public void setUseHashlookup(boolean enable) {
	Assert.isTrue(getInput() == null, "Can only enable the hash look up before input has been set");
	if (enable) {
		elementMap= new CustomHashtable(comparer);
	} else {
		elementMap= null;
	}	
}
/**
 * Sets the comparator to use for comparing elements,
 * or <code>null</code> to use the default <code>equals</code> and
 * <code>hashCode</code> methods on the elements themselves.
 * 
 * @param comparator the comparator to use for comparing elements
 *   or <code>null</code> 
 */
public void setComparer(IElementComparer comparer) {