content: /*******************************************************************************
   * Copyright (c) 2009, 2019 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;
  	}
  
  }
  