Bug 9159 Classpath wizard should not complain when adding missing source folder
Build 20020125 - Define a project A with source folder 'src1'. - Go to the .classpath file and edit it to insert one extra line: <classpathentry kind="src" path="src2"/> below the line referring to first source folder: <classpathentry kind="src" path="src1"/>. - Now, try to add this missing source folder 'src2', it isn't allowed by the wizard, one has to add a basic folder instead. Note: It is not such an uncommon scenario, the classpath modification could simply occur by catching up with a shared classpath having one more source folder on it, and which is locally missing.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/BuildPathsBlock.java
public static interface IRemoveOldBinariesQuery {
		
		public static int YES= 0;
		public static int NO= 1;
		public static int CANCEL= 2;
		
		/**
		 * Do the callback. Returns YES, NO, CANCEL to decide if .class files should be removed from the
		 * old output location.
		 */
		int doQuery(IPath oldOutputLocation);
		
	}
	private IWorkspaceRoot fWorkspaceRoot;
	private CheckedListDialogField fClassPathList;
	private StringButtonDialogField fBuildPathDialogField;
	
	private StatusInfo fClassPathStatus;
	private StatusInfo fBuildPathStatus;