关于BigDecimal的一些常用基本操作记录
1 BigDecimal b1 = new BigDecimal("1.124");
2 BigDecimal b2 = new BigDecimal("1.125");
3 BigDecimal b3 = new BigDecimal("1.126");
4 BigDecimal b4 = new BigDecimal("-1.126");
5 BigDecimal b5 = new BigDecimal("-1.123");
6 //加法
7 b1.add(b2);
8 //减法
9 b1.subtract(b2);
10 //乘法
11 b1.multiply(b2);
12 //除法(关于其小数保留下面统一解释)
13 b1.divide(b3, 2, BigDecimal.ROUND_UP);
14 //比较大小 (通过返回值区分 =0 相等， =1 前者大， =-1 后者大 )
15 b1.compareTo(b2);
16
17 //保留小数位与解释
18
19 /**
20 * 始终对非零舍弃部分前面的数字加1
21 *
22 * b1 1.124, b2 1.125, b3 1.126, b4 -1.126, b5 -1.123
23 */
24 System.out.println(b1.setScale(2, BigDecimal.ROUND_UP)); //1.13
25 System.out.println(b2.setScale(2, BigDecimal.ROUND_UP)); //1.13
26 System.out.println(b3.setScale(2, BigDecimal.ROUND_UP)); //1.13
27 System.out.println(b4.setScale(2, BigDecimal.ROUND_UP)); //-1.13
28 System.out.println(b5.setScale(2, BigDecimal.ROUND_UP)); //-1.13
29 /**
30 * 从不对舍弃部分前面的数字加1
31 *
32 * b1 1.124, b2 1.125, b3 1.126, b4 -1.126, b5 -1.123
33 */
34 System.out.println(b1.setScale(2, BigDecimal.ROUND_DOWN)); //1.12
35 System.out.println(b2.setScale(2, BigDecimal.ROUND_DOWN)); //1.12
36 System.out.println(b3.setScale(2, BigDecimal.ROUND_DOWN)); //1.12
37 System.out.println(b4.setScale(2, BigDecimal.ROUND_DOWN)); //-1.12
38 System.out.println(b5.setScale(2, BigDecimal.ROUND_DOWN)); //-1.12
39 /**
40 * 如果 BigDecimal 为正，则舍入行为与 ROUND_UP 相同
41 * 如果为负，则舍入行为与 ROUND_DOWN 相同
42 *
43 * b1 1.124, b2 1.125, b3 1.126, b4 -1.126, b5 -1.123
44 */
45 System.out.println(b1.setScale(2, BigDecimal.ROUND_CEILING)); //1.13
46 System.out.println(b2.setScale(2, BigDecimal.ROUND_CEILING)); //1.13
47 System.out.println(b3.setScale(2, BigDecimal.ROUND_CEILING)); //1.13
48 System.out.println(b4.setScale(2, BigDecimal.ROUND_CEILING)); //-1.12
49 System.out.println(b5.setScale(2, BigDecimal.ROUND_CEILING)); //-1.12
50 /**
51 * 如果 BigDecimal 为正，则舍入行为与 ROUND_DOWN 相同
52 * 如果为负，则舍入行为与 ROUND_UP 相同
53 *
54 * b1 1.124, b2 1.125, b3 1.126, b4 -1.126, b5 -1.123
55 */
56 System.out.println(b1.setScale(2, BigDecimal.ROUND_FLOOR)); //1.12
57 System.out.println(b2.setScale(2, BigDecimal.ROUND_FLOOR)); //1.12
58 System.out.println(b3.setScale(2, BigDecimal.ROUND_FLOOR)); //1.12
59 System.out.println(b4.setScale(2, BigDecimal.ROUND_FLOOR)); //-1.13
60 System.out.println(b5.setScale(2, BigDecimal.ROUND_FLOOR)); //-1.13
61 /**
62 * 如果舍弃部分 >= 0.5，则舍入行为与 ROUND_UP 相同;否则舍入行为与 ROUND_DOWN 相同
63 *
64 * b1 1.124, b2 1.125, b3 1.126, b4 -1.126, b5 -1.123
65 */
66 System.out.println(b1.setScale(2, BigDecimal.ROUND_HALF_UP)); //1.12
67 System.out.println(b2.setScale(2, BigDecimal.ROUND_HALF_UP)); //1.13
68 System.out.println(b3.setScale(2, BigDecimal.ROUND_HALF_UP)); //1.13
69 System.out.println(b4.setScale(2, BigDecimal.ROUND_HALF_UP)); //-1.13
70 System.out.println(b5.setScale(2, BigDecimal.ROUND_HALF_UP)); //-1.12
71 /**
72 * 如果舍弃部分 > 0.5，则舍入行为与 ROUND_UP 相同;否则舍入行为与 ROUND_DOWN 相同(五舍六入)。
73 *
74 * b1 1.124, b2 1.125, b3 1.126, b4 -1.126, b5 -1.123
75 */
76 System.out.println(b1.setScale(2, BigDecimal.ROUND_HALF_DOWN)); //1.12
77 System.out.println(b2.setScale(2, BigDecimal.ROUND_HALF_DOWN)); //1.12
78 System.out.println(b3.setScale(2, BigDecimal.ROUND_HALF_DOWN)); //1.13
79 System.out.println(b4.setScale(2, BigDecimal.ROUND_HALF_DOWN)); //-1.13
80 System.out.println(b5.setScale(2, BigDecimal.ROUND_HALF_DOWN)); //-1.12