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/**
* Copyright 2017 VMware, Inc.
*
* Licensed 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
*
* https://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.
*/
package io.micrometer.core.instrument.util;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.text.NumberFormat;
import java.util.Locale;
/**
* Commonly used formatting of floating-point values used when writing custom exposition to various monitoring systems.
*
* @author Jon Schneider
*/
public final class DoubleFormat {
/**
* Because NumberFormat is not thread-safe we cannot share instances across threads. Use a ThreadLocal to
* create one per thread as this seems to offer a significant performance improvement over creating one per-thread:
* https://stackoverflow.com/a/1285297/2648
* https://github.com/indeedeng/java-dogstatsd-client/issues/4
*/
private static final ThreadLocal DECIMAL_OR_NAN = ThreadLocal.withInitial(() -> {
// Always create the formatter for the US locale in order to avoid this bug:
// https://github.com/indeedeng/java-dogstatsd-client/issues/3
final NumberFormat numberFormatter = NumberFormat.getInstance(Locale.US);
numberFormatter.setGroupingUsed(false);
numberFormatter.setMaximumFractionDigits(6);
// we need to specify a bucket for Double.NaN that is recognized by dogStatsD
if (numberFormatter instanceof DecimalFormat) { // better safe than a runtime error
final DecimalFormat decimalFormat = (DecimalFormat) numberFormatter;
final DecimalFormatSymbols symbols = decimalFormat.getDecimalFormatSymbols();
symbols.setNaN("NaN");
decimalFormat.setDecimalFormatSymbols(symbols);
}
return numberFormatter;
});
private static final ThreadLocal WHOLE_OR_DECIMAL = ThreadLocal.withInitial(() -> {
// the following will ensure a dot ('.') as decimal separator
DecimalFormatSymbols otherSymbols = new DecimalFormatSymbols(Locale.US);
return new DecimalFormat("##0.######", otherSymbols);
});
private static final ThreadLocal DECIMAL = ThreadLocal.withInitial(() -> {
// the following will ensure a dot ('.') as decimal separator
DecimalFormatSymbols otherSymbols = new DecimalFormatSymbols(Locale.US);
return new DecimalFormat("##0.0#####", otherSymbols);
});
private DoubleFormat() {
}
/**
* @param d Number to format.
* @return A stringified version of the number that uses a decimal representation or the word "NaN".
*/
public static String decimalOrNan(double d) {
return DECIMAL_OR_NAN.get().format(d);
}
/**
* @param d Number to format.
* @return A stringified version of the number that only uses a decimal representation if the number is not
* whole.
* @deprecated since 1.0.11 in favour of {@link #wholeOrDecimal(double)}
*/
@Deprecated
public static String decimalOrWhole(double d) {
return WHOLE_OR_DECIMAL.get().format(d);
}
/**
* @param d Number to format.
* @return A stringified version of the number that only uses a decimal representation if the number is not
* whole.
*/
public static String decimal(double d) {
return DECIMAL.get().format(d);
}
/**
* @param d Number to format.
* @return A stringified version of the number that only uses a decimal representation if the number is not
* whole.
*/
public static String wholeOrDecimal(double d) {
return WHOLE_OR_DECIMAL.get().format(d);
}
}