# StringPool.java

    /*******************************************************************************
     * Copyright (c) 2009, 2013 Mountainminds GmbH & Co. KG and Contributors
     * 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:
     *    Brock Janiczak - analysis and concept
     *    Marc R. Hoffmann - initial API and implementation
     *
     *******************************************************************************/
    package org.jacoco.core.internal.analysis;

    import java.util.HashMap;
    import java.util.Map;

    /**
     * Utility to normalize {@link String} instances in a way that if
     * <code>equals()</code> is <code>true</code> for two strings they will be
     * represented the same instance. While this is exactly what
     * {@link String#intern()} does, this implementation avoids VM specific side
     * effects and is supposed to be faster, as neither native code is called nor
     * synchronization is required for concurrent lookup.
     */
    public final class StringPool {

    	private static final String[] EMPTY_ARRAY = new String[0];

    	private final Map<String, String> pool = new HashMap<String, String>(1024);

    	/**
    	 * Returns a normalized instance that is equal to the given {@link String} .
    	 *
    	 * @param s
    	 *            any string or <code>null</code>
    	 * @return normalized instance or <code>null</code>
    	 */
    	public String get(final String s) {
    		if (s == null) {
    			return null;
    		}
    		final String norm = pool.get(s);
    		if (norm == null) {
    			pool.put(s, s);
    			return s;
    		}
    		return norm;
    	}

    	/**
    	 * Returns a modified version of the array with all string slots normalized.
    	 * It is up to the implementation to replace strings in the array instance
    	 * or return a new array instance.
    	 *
    	 * @param arr
    	 *            String array or <code>null</code>
    	 * @return normalized instance or <code>null</code>
    	 */
    	public String[] get(final String[] arr) {
    		if (arr == null) {
    			return null;
    		}
    		if (arr.length == 0) {
    			return EMPTY_ARRAY;
    		}
    		for (int i = 0; i < arr.length; i++) {
    			arr[i] = get(arr[i]);
    		}
    		return arr;
    	}

    }