DoubleUtils.java

/*
 * Tencent is pleased to support the open source community by making
 * Tencent GT (Version 2.4 and subsequent versions) available.
 *
 * Notwithstanding anything to the contrary herein, any previous version
 * of Tencent GT shall not be subject to the license hereunder.
 * All right, title, and interest, including all intellectual property rights,
 * in and to the previous version of Tencent GT (including any and all copies thereof)
 * shall be owned and retained by Tencent and subject to the license under the
 * Tencent GT End User License Agreement (http://gt.qq.com/wp-content/EULA_EN.html).
 * 
 * Copyright (C) 2015 THL A29 Limited, a Tencent company. All rights reserved.
 * 
 * Licensed under the MIT License (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of the License at
 * 
 * http://opensource.org/licenses/MIT
 * 
 * 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 com.tencent.wstt.gt.utils;

import java.math.BigDecimal;

/**
 * Double数据的操作 使用Java，double 进行运算时，经常出现精度丢失的问题，总是在一个正确的结果左右偏0.0000**1。
 * 特别在实际项目中，通过一个公式校验该值是否大于0，如果大于0我们会做一件事情，小于0我们又处理其他事情。
 * 这样的情况通过double计算出来的结果去和0比较大小，尤其是有小数点的时候，经常会因为精度丢失而导致程序处理流程出错。
 */
public class DoubleUtils {
	/**
	 * double 乘法
	 * 
	 * @param d1
	 * @param d2
	 * @return
	 */
	public static double mul(double d1, double d2) {
		BigDecimal bd1 = new BigDecimal(Double.toString(d1));
		BigDecimal bd2 = new BigDecimal(Double.toString(d2));
		
		try
		{
			return bd1.multiply(bd2).doubleValue();
		} catch (Exception e)
		{
			// 根据bugly观测，在进入GTOpMulPerfActivity页时有极小概率crash，故加上异常保护
			// @see http://bugly.qq.com/detail?app=900010910&pid=1&ii=152#stack
			e.printStackTrace();
			return 0;
		}
	}

	/**
	 * double 除法
	 * 
	 * @param d1
	 * @param d2
	 * @param scale
	 *            四舍五入 小数点位数
	 * @return
	 */
	public static double div(double d1, double d2, int scale) {
		// 当然在此之前，你要判断分母是否为0，
		// 为0你可以根据实际需求做相应的处理

		BigDecimal bd1 = new BigDecimal(Double.toString(d1));
		BigDecimal bd2 = new BigDecimal(Double.toString(d2));
//		return bd1.divide(bd2, scale, BigDecimal.ROUND_HALF_UP).doubleValue();
		// 直接向下取整，保持和UI展示一致
		try
		{
			return bd1.divide(bd2, scale, BigDecimal.ROUND_DOWN).doubleValue();
		} catch (Exception e)
		{
			// 根据bugly观测，在进入GTOpMulPerfActivity页时有极小概率crash，故加上异常保护
			// @see http://bugly.qq.com/detail?app=900010910&pid=1&ii=46#stack
			e.printStackTrace();
			return 0;
		}
		
	}

}