BigDecimal类的加减乘除(

BigDecimal类型(+ - * /)所用的属性

11.10 BigDecimal类

对于不需要任何准确计算精度的数字可以直接使用float或double，但是如果需要精确计算的结果，则必须使用BigDecimal类，而且使用BigDecimal类也可以进行大数的操作。BigDecimal类的常用方法如表11-15所示。

表11-15 BigDecimal类的常用方法

序号	方 <wbr><wbr><wbr></wbr></wbr></wbr>法	类型	描 <wbr><wbr><wbr></wbr></wbr></wbr>述
1	public BigDecimal(double val)	构造	将double表示形式转换 为BigDecimal
2	public BigDecimal(int val)	构造	将int表示形式转换为 BigDecimal
3	public BigDecimal(String val)	构造	将字符串表示 形式转换为BigDecimal
4	public BigDecimal add(BigDecimal augend)	普通	加法
5	public BigDecimal subtract(BigDecimal subtrahend)	普通	减法
6	public BigDecimal multiply(BigDecimal multiplicand)	普通	乘法
7	public BigDecimal divide(BigDecimal divisor)	普通	除法

范例：进行四舍五入的四则运算

1. package org.lxh.demo11.numberdemo;
2. import java.math.BigDecimal;
3. class MyMath {
4. <wbr><wbr><wbr><wbr><strong><span style="color:#006699">public</span> <span style="color:#006699"> static</span> <span style="color:#006699">double</span></strong> add(<strong><span style="color:#006699">double</span></strong> d1, <strong><span style="color:#006699">double</span></strong> d2)<br> { <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="color:#008200">// 进行加法运算</span> </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
5. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>BigDecimal b1 = <strong><span style="color:#006699">new</span></strong> BigDecimal(d1); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
6. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>BigDecimal b2 = <strong><span style="color:#006699">new</span></strong> BigDecimal(d2); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
7. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><strong><span style="color:#006699">return</span></strong> b1.add(b2).doubleValue(); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
8. <wbr><wbr><wbr><wbr>} </wbr></wbr></wbr></wbr>
9. <wbr><wbr><wbr><wbr><strong><span style="color:#006699">public</span> <span style="color:#006699"> static</span> <span style="color:#006699">double</span></strong> sub(<strong><span style="color:#006699">double</span></strong> d1, <strong><span style="color:#006699">double</span></strong> d2)<br> { <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="color:#008200">// 进行减法运算</span> </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
10. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>BigDecimal b1 = <strong><span style="color:#006699">new</span></strong> BigDecimal(d1); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
11. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>BigDecimal b2 = <strong><span style="color:#006699">new</span></strong> BigDecimal(d2); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
12. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><strong><span style="color:#006699">return</span></strong> b1.subtract(b2).doubleValue(); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
13. <wbr><wbr><wbr><wbr>} </wbr></wbr></wbr></wbr>
14. <wbr><wbr><wbr><wbr><strong><span style="color:#006699">public</span> <span style="color:#006699"> static</span> <span style="color:#006699">double</span></strong> mul(<strong><span style="color:#006699">double</span></strong> d1, <strong><span style="color:#006699">double</span></strong> d2)<br> { <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="color:#008200">// 进行乘法运算</span> </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
15. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>BigDecimal b1 = <strong><span style="color:#006699">new</span></strong> BigDecimal(d1); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
16. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>BigDecimal b2 = <strong><span style="color:#006699">new</span></strong> BigDecimal(d2); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
17. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><strong><span style="color:#006699">return</span></strong> b1.multiply(b2).doubleValue(); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
18. <wbr><wbr><wbr><wbr>} </wbr></wbr></wbr></wbr>
19. <wbr><wbr><wbr><wbr><strong><span style="color:#006699">public</span> <span style="color:#006699"> static</span> <span style="color:#006699">double</span></strong> div(<strong><span style="color:#006699">double</span></strong> d1,<br><strong><span style="color:#006699">double</span></strong> d2,<strong><span style="color:#006699">int</span></strong> len) {<span style="color:#008200">// 进行除法运算</span> </wbr></wbr></wbr></wbr>
20. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>BigDecimal b1 = <strong><span style="color:#006699">new</span></strong> BigDecimal(d1); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
21. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>BigDecimal b2 = <strong><span style="color:#006699">new</span></strong> BigDecimal(d2); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
22. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><strong><span style="color:#006699">return</span></strong> b1.divide(b2,len,BigDecimal.<br> ROUND_HALF_UP).doubleValue(); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
23. <wbr><wbr><wbr><wbr>} </wbr></wbr></wbr></wbr>
24. <wbr><wbr><wbr><wbr><strong><span style="color:#006699">public</span> <span style="color:#006699"> static</span> <span style="color:#006699">double</span></strong> round(<strong><span style="color:#006699">double</span></strong> d,<br><strong><span style="color:#006699">int</span></strong> len) { <wbr><wbr><wbr><wbr><wbr><span style="color:#008200">// 进行四舍五入</span> </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
25. 操作
26. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>BigDecimal b1 = <strong><span style="color:#006699">new</span></strong> BigDecimal(d); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
27. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>BigDecimal b2 = <strong><span style="color:#006699">new</span></strong> BigDecimal(<span style="color:#c00000">1</span>); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
28. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="color:#008200">// 任何一个数字除以1都是原数字</span> </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
29. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="color:#008200">// ROUND_HALF_UP是BigDecimal的一个常量，<br> 表示进行四舍五入的操作</span> </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
30. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><strong><span style="color:#006699">return</span></strong> b1.divide(b2, len,BigDecimal.<br> ROUND_HALF_UP).doubleValue(); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
31. <wbr><wbr><wbr><wbr>} </wbr></wbr></wbr></wbr>
32. }
33. public class BigDecimalDemo01 {
34. <wbr><wbr><wbr><wbr><strong><span style="color:#006699">public</span> <span style="color:#006699"> static</span> <span style="color:#006699">void</span></strong> main(String[] args) { </wbr></wbr></wbr></wbr>
35. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>System.out.println(<span style="color:#0000ff">"加法运算："</span> +<br> MyMath.round(MyMath.add(<span style="color:#c00000">10.345</span>, </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
36. 3.333), 1));
37. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>System.out.println(<span style="color:#0000ff">"乘法运算："</span> +<br> MyMath.round(MyMath.mul(<span style="color:#c00000">10.345</span>, </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
38. 3.333), 3));
39. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>System.out.println(<span style="color:#0000ff">"除法运算："</span> +<br> MyMath.div(<span style="color:#c00000">10.345</span>, <span style="color:#c00000"> 3.333</span>, <span style="color:#c00000">3</span>)); </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
40. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>System.out.println(<span style="color:#0000ff">"减法运算："</span> +<br> MyMath.round(MyMath.sub(<span style="color:#c00000">10.345</span>, </wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
41. 3.333), 3));
42. <wbr><wbr><wbr><wbr>} </wbr></wbr></wbr></wbr>
43. }