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/*
* 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 {@code DecimalFormat} instance. {@code 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 {@code ThreadLocal}.
*/
public class 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 {@code 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();
}
}
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