java - BigDecimal movePointRight 和 scaleByPowerOfTen 有什么区别？

Question

使用以下代码:

BigDecimal x = new BigDecimal("34.5678");
BigDecimal a = x.movePointRight(3);
BigDecimal b = x.scaleByPowerOfTen(3);
BigDecimal c = x.movePointRight(-3);
BigDecimal d = x.scaleByPowerOfTen(-3);

a 和 b 都是 34567.8，c 和 d 都是 0.0345678。a.scale()和b.scale都是1，c.scale()和d.scale() 都是 7.

这两种方法在什么情况下会产生不同的结果？

Answer 1

• movePointRight 将防止出现负比例(如果它导致负比例)。
• scaleByPowerOfTen 不会阻止这种情况。

示例代码:

import java.math.BigDecimal;

public class BigDecimalScale {
  public static void main(String... args) {
    long base = 12345;
    int scale = 4;

    BigDecimal number = BigDecimal.valueOf(base, scale);
    System.out.println(number);
    BigDecimal pointRight = number.movePointRight(5);
    System.out.println(pointRight + "; my scale is " + pointRight.scale());
    BigDecimal scaleBy = number.scaleByPowerOfTen(5);
    System.out.println(scaleBy + "; my scale is " + scaleBy.scale());
  }
}

结果:

1.2345
123450; my scale is 0
1.2345E+5; my scale is -1