Bug 52064 Content assist in "New Class" Dialog shows interfaces
Content Assist is available for the superclass in M7. However it also lists interfaces. If an interface is selected, the generated class "extends" it instead of "implementing" it.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/wizards/NewTypeWizardPage.java
* @param interfacesNames a list of super interface. The method requires that
	 * the list's elements are of type <code>String</code>
	 * @param canBeModified if <code>true</code> the super interface field is
	 * editable; otherwise it is read-only.
	 */	
	public void setSuperInterfaces(List interfacesNames, boolean canBeModified) {
		fSuperInterfacesDialogField.setElements(interfacesNames);
		fSuperInterfacesDialogField.setEnabled(canBeModified);
	}
			
	/**
	 * Returns the resource handle that corresponds to the compilation unit to was or
	 * will be created or modified.
	 * @return A resource or null if the page contains illegal values.
	 * @since 3.0
	 */
	public IResource getModifiedResource() {
		IType enclosing= getEnclosingType();
		if (enclosing != null) {
			return enclosing.getResource();
		}
		IPackageFragment pack= getPackageFragment();
		if (pack != null) {
			return pack.getCompilationUnit(getTypeName() + ".java").getResource(); 
		}
		return null;
	}