Editor.java

package edu.wlu.cs.levy.CG;

public interface Editor<T> {

	public T edit(T current) throws KeyDuplicateException;

	public static abstract class BaseEditor<T> implements Editor<T> {

		final T val;

		public BaseEditor(T val) {
			this.val = val;
		}

		public abstract T edit(T current) throws KeyDuplicateException;
	}

	public static class Inserter<T> extends BaseEditor<T> {

		public Inserter(T val) {
			super(val);
		}

		@Override
		public T edit(T current) throws KeyDuplicateException {
			if (current == null) {
				return this.val;
			}
			throw new KeyDuplicateException();
		}
	}

	public static class OptionalInserter<T> extends BaseEditor<T> {

		public OptionalInserter(T val) {
			super(val);
		}

		@Override
		public T edit(T current) {
			return current == null ? this.val : current;
		}
	}

	public static class Replacer<T> extends BaseEditor<T> {

		public Replacer(T val) {
			super(val);
		}

		@Override
		public T edit(T current) {
			return this.val;
		}
	}
}