| /******************************************************************************* |
| * Copyright (c) 2005, 2015 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 - Initial API and implementation |
| *******************************************************************************/ |
| package org.eclipse.core.internal.preferences; |
| |
| import java.util.HashMap; |
| |
| /** |
| * A string pool is used for sharing strings in a way that eliminates duplicate |
| * equal strings. A string pool instance can be maintained over a long period |
| * of time, or used as a temporary structure during a string sharing pass over |
| * a data structure. |
| * <p> |
| * This class is not intended to be subclassed by clients. |
| * </p> |
| * |
| * Note: This class is copied from org.eclipse.core.resources |
| * |
| * @since 3.1 |
| */ |
| public final class StringPool { |
| private int savings; |
| private final HashMap<String, String> map = new HashMap<>(); |
| |
| /** |
| * Adds a <code>String</code> to the pool. Returns a <code>String</code> |
| * that is equal to the argument but that is unique within this pool. |
| * @param string The string to add to the pool |
| * @return A string that is equal to the argument. |
| */ |
| public String add(String string) { |
| if (string == null) |
| return string; |
| Object result = map.get(string); |
| if (result != null) { |
| if (result != string) |
| savings += 44 + 2 * string.length(); |
| return (String) result; |
| } |
| map.put(string, string); |
| return string; |
| } |
| |
| /** |
| * Returns an estimate of the size in bytes that was saved by sharing strings in |
| * the pool. In particular, this returns the size of all strings that were added to the |
| * pool after an equal string had already been added. This value can be used |
| * to estimate the effectiveness of a string sharing operation, in order to |
| * determine if or when it should be performed again. |
| * |
| * In some cases this does not precisely represent the number of bytes that |
| * were saved. For example, say the pool already contains string S1. Now |
| * string S2, which is equal to S1 but not identical, is added to the pool five |
| * times. This method will return the size of string S2 multiplied by the |
| * number of times it was added, even though the actual savings in this case |
| * is only the size of a single copy of S2. |
| */ |
| public int getSavedStringCount() { |
| return savings; |
| } |
| } |