public class EntryPoint implements IJavaCompletionProposalComputer {

	 /**
     * A cache for type hierarchies to avoid unnecessary computations
     */
    private final Map<IType, ITypeHierarchy> hierarchies = new HashMap<IType, ITypeHierarchy>();

	@Override
	public List<?> computeCompletionProposals(
			ContentAssistInvocationContext context, IProgressMonitor monitor) {
		
		final JavaContentAssistInvocationContext jctx = (JavaContentAssistInvocationContext) context;
		try {
			IType lookupContext = jctx.getCompilationUnit().getJavaProject().findType("java.lang.String");
			IType typeToCheck = jctx.getCompilationUnit().getJavaProject().findType("org.eclipse.ui.IWorkbench");
			System.out.println(this.isSubtype(lookupContext, typeToCheck) + " " + this.isSupertype(lookupContext, typeToCheck));
			
		} catch (JavaModelException e) {
			e.printStackTrace();
		}
		return Collections.emptyList();
	}

	@Override
	public List<?> computeContextInformation(
			ContentAssistInvocationContext context, IProgressMonitor monitor) {
		return Collections.emptyList();
	}

	@Override
	public String getErrorMessage() {
		return null;
	}

	@Override
	public void sessionEnded() {
		
	}

	@Override
	public void sessionStarted() {
	}
	
	
	/**
     * Tests for subtype relation between two types in a (once created) type hierarchy
     * @param context base type
     * @param subtype type to test to be a subtype or not
     * @return true, in case of subtype relation, else false
     * @throws JavaModelException
     * @see {@link #isSupertype(IType, IType)}
     */
	public boolean isSubtype(IType context, IType subtype) throws JavaModelException {
		long i = System.currentTimeMillis();
		ITypeHierarchy hierarchy = hierarchies.get(context);
		if (hierarchy == null) {
			hierarchy = context.newTypeHierarchy(new NullProgressMonitor());
			synchronized (hierarchies) {
				hierarchies.put(context, hierarchy);
			}
		}
		IType subtypes[] = hierarchy.getAllSubtypes(context);
		boolean ret = Arrays.asList(subtypes).contains(subtype);
		System.out.println("subtype: " + (System.currentTimeMillis() - i) + " " + context.getFullyQualifiedName() + " - " + subtype.getElementName());
		return ret;
	}

    /**
     * Tests for supertype relation between two types in a (once created) type hierarchy
     * @param context concrete type
     * @param subtype type to test to be a supertype or not
     * @return true, in case of supertype relation, else false
     * @throws JavaModelException
     * @see {@link #isSubtype(IType, IType)}
     */
	public boolean isSupertype(IType context, IType subtype) throws JavaModelException {
		long i = System.currentTimeMillis();
		ITypeHierarchy hierarchy = hierarchies.get(subtype);
		if (hierarchy == null) {
			hierarchy = subtype.newTypeHierarchy(new NullProgressMonitor());
			synchronized (hierarchies) {
				hierarchies.put(subtype, hierarchy);
			}
		}
		
		IType subtypes[] = hierarchy.getAllSubtypes(subtype);
		boolean ret = Arrays.asList(subtypes).contains(context);
		System.out.println("supertype: " + (System.currentTimeMillis() - i) + " " + context.getFullyQualifiedName() + " - " + subtype.getElementName());
		return ret;
	}
}