net.grinder.util.SignificantFigureFormat Maven / Gradle / Ivy
// Copyright (C) 2000 - 2008 Philip Aston
// All rights reserved.
//
// This file is part of The Grinder software distribution. Refer to
// the file LICENSE which is part of The Grinder distribution for
// licensing details. The Grinder distribution is available on the
// Internet at http://grinder.sourceforge.net/
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
// OF THE POSSIBILITY OF SUCH DAMAGE.
package net.grinder.util;
import java.text.DecimalFormat;
import java.text.FieldPosition;
/**
* Java doesn't provide a NumberFormatter which understands
* significant figures, this is a cheap and cheerful one. Not
* extensively tested.
*
* @author Philip Aston
*/
public class SignificantFigureFormat extends DecimalFormat {
private static final long serialVersionUID = 1;
private static final int s_decimalPlaces = 40;
private final int m_significantFigures;
/**
* Constructor.
*
* @param significantFigures Number of significant figures.
*/
public SignificantFigureFormat(int significantFigures) {
// 40 DP, should match value of s_decimalPlaces.
super("0.0000000000000000000000000000000000000000");
m_significantFigures = significantFigures;
}
private static int boundingPowerOfTen(double number) {
if (number == 0d ||
Double.isInfinite(number) ||
Double.isNaN(number)) {
return 1;
}
final double abs = Math.abs(number);
int i = 0;
double x = 1;
if (abs < 1) {
while (x > abs) {
x /= 10;
--i;
}
return i + 1;
}
else {
while (!(x > abs)) {
x *= 10;
++i;
}
return i;
}
}
/**
* Almost certainly doesn't set position correctly.
*
* @param number Number to format.
* @param buffer Buffer to append result to.
* @param position Field position.
* @return a StringBuffer value
*/
public StringBuffer format(double number, StringBuffer buffer,
FieldPosition position) {
if (Double.isInfinite(number) ||
Double.isNaN(number)) {
return super.format(number, buffer, position);
}
final int shift = boundingPowerOfTen(number) - m_significantFigures;
final double factor = Math.pow(10, shift);
super.format(factor * Math.round(number / factor), buffer, position);
final int truncate =
shift < 0 ? s_decimalPlaces + shift : s_decimalPlaces + 1;
buffer.setLength(buffer.length() - truncate);
return buffer;
}
/**
* Almost certainly doesn't set position correctly.
*
* @param number Number to format.
* @param buffer Buffer to append result to.
* @param position Field position.
* @return a StringBuffer value
*/
public StringBuffer format(long number, StringBuffer buffer,
FieldPosition position) {
return format((double)number, buffer, position);
}
/**
* {@inheritDoc}
*/
@Override public boolean equals(Object o) {
if (o == null) {
return false;
}
if (o == this) {
return true;
}
return
super.equals(o) &&
m_significantFigures == ((SignificantFigureFormat)o).m_significantFigures;
}
/**
* {@inheritDoc}
*/
@Override public int hashCode() {
return super.hashCode();
}
}