HashtableOfInt.java

/*******************************************************************************
 * Copyright (c) 2000, 2009 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jdt.internal.compiler.util;

/**
 * Hashtable for non-zero int keys.
 */

public final class HashtableOfInt {
	// to avoid using Enumerations, walk the individual tables skipping nulls
	public int[] keyTable;

	public Object[] valueTable;

	public int elementSize; // number of elements in the table

	int threshold;

	public HashtableOfInt() {
		this(13);
	}

	public HashtableOfInt(int size) {
		this.elementSize= 0;
		this.threshold= size; // size represents the expected number of elements
		int extraRoom= (int)(size * 1.75f);
		if (this.threshold == extraRoom)
			extraRoom++;
		this.keyTable= new int[extraRoom];
		this.valueTable= new Object[extraRoom];
	}

	public boolean containsKey(int key) {
		int length= this.keyTable.length, index= key % length;
		int currentKey;
		while ((currentKey= this.keyTable[index]) != 0) {
			if (currentKey == key)
				return true;
			if (++index == length) {
				index= 0;
			}
		}
		return false;
	}

	public Object get(int key) {
		int length= this.keyTable.length, index= key % length;
		int currentKey;
		while ((currentKey= this.keyTable[index]) != 0) {
			if (currentKey == key)
				return this.valueTable[index];
			if (++index == length) {
				index= 0;
			}
		}
		return null;
	}

	public Object put(int key, Object value) {
		int length= this.keyTable.length, index= key % length;
		int currentKey;
		while ((currentKey= this.keyTable[index]) != 0) {
			if (currentKey == key)
				return this.valueTable[index]= value;
			if (++index == length) {
				index= 0;
			}
		}
		this.keyTable[index]= key;
		this.valueTable[index]= value;

		// assumes the threshold is never equal to the size of the table
		if (++this.elementSize > this.threshold)
			rehash();
		return value;
	}

	private void rehash() {
		HashtableOfInt newHashtable= new HashtableOfInt(this.elementSize * 2); // double the number of expected elements
		int currentKey;
		for (int i= this.keyTable.length; --i >= 0;)
			if ((currentKey= this.keyTable[i]) != 0)
				newHashtable.put(currentKey, this.valueTable[i]);

		this.keyTable= newHashtable.keyTable;
		this.valueTable= newHashtable.valueTable;
		this.threshold= newHashtable.threshold;
	}

	public int size() {
		return this.elementSize;
	}

	public String toString() {
		String s= ""; //$NON-NLS-1$
		Object object;
		for (int i= 0, length= this.valueTable.length; i < length; i++)
			if ((object= this.valueTable[i]) != null)
				s+= this.keyTable[i] + " -> " + object.toString() + "\n"; //$NON-NLS-2$ //$NON-NLS-1$
		return s;
	}
}