Java double相减误差 Java用BigDecimal解决double类型相减时可能存在的误差
liuhmmjj 人气:0double类型的两个数相减可能存在误差,比如System.out.println(2099 - 1999.9);的结果为99.09999999999991
可以用BigDecimal解决:
public class TestDouble { //两个Double数相减 public static Double sub(Double d1, Double d2) { if (d1 == null || d2 == null) { return null; } BigDecimal b1 = new BigDecimal(d1.toString()); BigDecimal b2 = new BigDecimal(d2.toString()); return b1.subtract(b2).doubleValue(); } //两个Double数相加 public static Double add(Double d1, Double d2) { if (d1 == null || d2 == null) { return null; } BigDecimal b1 = new BigDecimal(d1.toString()); BigDecimal b2 = new BigDecimal(d2.toString()); return b1.add(b2).doubleValue(); } //两个Double数相除,并保留scale位小数 public static Double div(Double d1, Double d2, int scale) { if (d1 == null || d2 == null || scale < 0) { return null; } BigDecimal b1 = new BigDecimal(d1.toString()); BigDecimal b2 = new BigDecimal(d2.toString()); return b1.divide(b2, scale, BigDecimal.ROUND_HALF_UP).doubleValue(); } // 两个Double数相乘 public static Double mul(Double d1, Double d2) { if (d1 == null || d2 == null) { return null; } BigDecimal b1 = new BigDecimal(d1.toString()); BigDecimal b2 = new BigDecimal(d2.toString()); return b1.multiply(b2).doubleValue(); } /** * 遇到.5的情况时往上近似 * * @param d * @param scale * @return */ public static Double setDoubleScale(Double d, int scale) { if (d == null || scale < 0) { return null; } BigDecimal b = new BigDecimal(d); return b.setScale(scale, BigDecimal.ROUND_HALF_UP).doubleValue(); } public static void main(String[] args) { Double d1 = 2099d; Double d2 = 1999.999; System.out.println(d1 - d2); System.out.println(sub(d1, d2)); System.out.println("------------------------------------"); System.out.println(d1 * d2); System.out.println(mul(d1, d2)); System.out.println("------------------------------------"); System.out.println(d1/d2); System.out.println(div(d1,d2,4)); } }
结果:
99.00099999999998
99.001
------------------------------------
4197997.901
4197997.901
------------------------------------
1.0495005247502625
1.0495
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