/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /* $Id$ */ package org.apache.fop.util; import java.text.DecimalFormat; import java.text.DecimalFormatSymbols; import java.util.Locale; /** * This class provides a cache for {@link DecimalFormat} instance. {@link DecimalFormat} itself * is not thread-safe but since FOP needs to format a lot of numbers the same way, it shall * be cached in a {@link ThreadLocal}. */ public final class DecimalFormatCache { private DecimalFormatCache() { } private static final String BASE_FORMAT = "0.################"; private static class DecimalFormatThreadLocal extends ThreadLocal { private int dec; public DecimalFormatThreadLocal(int dec) { this.dec = dec; } protected synchronized Object initialValue() { String s = "0"; if (dec > 0) { s = BASE_FORMAT.substring(0, dec + 2); } DecimalFormat df = new DecimalFormat(s, new DecimalFormatSymbols(Locale.US)); return df; } }; //DecimalFormat is not thread-safe! private static final ThreadLocal[] DECIMAL_FORMAT_CACHE = new DecimalFormatThreadLocal[17]; static { for (int i = 0, c = DECIMAL_FORMAT_CACHE.length; i < c; i++) { DECIMAL_FORMAT_CACHE[i] = new DecimalFormatThreadLocal(i); } } /** * Returns a cached {@link DecimalFormat} instance for the given number of decimal digits. * @param dec the number of decimal digits. * @return the DecimalFormat instance */ public static DecimalFormat getDecimalFormat(int dec) { if (dec < 0 || dec >= DECIMAL_FORMAT_CACHE.length) { throw new IllegalArgumentException("Parameter dec must be between 1 and " + (DECIMAL_FORMAT_CACHE.length + 1)); } return (DecimalFormat)DECIMAL_FORMAT_CACHE[dec].get(); } }