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Appdapter Maven project including Java and Scala, produces jar, not bundle. Excludes concrete SLF4J binding.

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package org.appdapter.gui.util;

import java.io.PrintStream;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Vector;

public class PairTable {
	//Note: a "pair" is simply an array of 2 objects

	//object -> its brother
	Hashtable hash = new Hashtable();

	public PairTable() {
	}

	public void add(Object o1, Object o2) {
		if (o1 != null && o2 != null) {
			remove(o1);
			remove(o2);
			hash.put(o1, o2);
			hash.put(o2, o1);
		}
	}

	public int getPairCount() {
		return hash.size() / 2;
	}

	public boolean contains(Object o) {
		return hash.containsKey(o);
	}

	public Object findBrother(Object o1) {
		if (o1 == null)
			return null;
		else
			return hash.get(o1);
	}

	public void remove(Object o1) {
		Object o2 = findBrother(o1);
		if (o2 != null) {
			hash.remove(o1);
			hash.remove(o2);
		}
	}

	public Vector getPairs() {
		int size = hash.size() / 2;

		Vector pairs = new Vector();
		Vector accounted = new Vector();

		Enumeration keys = hash.keys();
		Object o1, o2;
		Object[] pair;
		while (keys.hasMoreElements()) {
			o1 = keys.nextElement();
			if (!accounted.contains(o1)) {
				o2 = findBrother(o1);
				pair = new Object[] { o1, o2 };
				pairs.addElement(pair);
				accounted.addElement(o2);
			}
		}
		return pairs;
	}

	public void list(PrintStream ps) {
		Enumeration enum0 = getPairs().elements();
		while (enum0.hasMoreElements()) {
			Object[] pair = (Object[]) enum0.nextElement();
			ps.println("[" + pair[0] + "] [" + pair[1] + "]");
		}
	}

	public static boolean isEqual(Object o1, Object o2) {
		if (o1 == null)
			return (o2 == null);
		else
			return (o1.equals(o2));
	}

	public void clear() {
		hash.clear();

	}
}