BigDecimal. Summary of setscale usage

1. ROUND_DOWN( Directly omit the contents after the specified number of digits )
   BigDecimal bigDecimal = new BigDecimal(“2.125456”).setScale(2, BigDecimal.ROUND_DOWN);

System.out.println(bigDecimal ); // result ：2.12

2. ROUND_UP（ Directly perform one bit processing on the content after the specified number of bits ）
   BigDecimal bigDecimal = new BigDecimal(“2.125456”).setScale(2, BigDecimal.ROUND_UP);

System.out.println(bigDecimal); // result ：2.13

3. ROUND_CEILING（ Positive numbers use ROUND_UP The rules , Negative numbers use ROUND_DOWN The rules ）
   BigDecimal bigDecimalA = new BigDecimal(“2.125456”).setScale(2, BigDecimal.ROUND_CEILING);

System.out.println(bigDecimalA);// result ：2.13

BigDecimal bigDecimalB = new BigDecimal("-2.125456").setScale(2, BigDecimal.ROUND_CEILING);

System.out.println(bigDecimalB);// result ：2.12

4. ROUND_FLOOR（ Positive numbers omit content , Negative numbers go down one digit ）
   BigDecimal bigDecimalA = new BigDecimal(“2.125456”).setScale(2, BigDecimal.ROUND_FLOOR);

System.out.println(bigDecimalA);// result ：2.12

BigDecimal bigDecimalB = new BigDecimal("-2.125456").setScale(2, BigDecimal.ROUND_FLOOR);

System.out.println(bigDecimalB);// result ：-2.13

5. ROUND_HALF_UP,ROUND_HALF_DOWN（ rounding ）
   BigDecimal bigDecimalA = new BigDecimal(“2.125456”).setScale(2, BigDecimal.ROUND_HALF_UP);

System.out.println(bigDecimalA);// result ：2.13

BigDecimal bigDecimalB = new BigDecimal("-2.125456").setScale(2, BigDecimal.ROUND_HALF_DOWN);

System.out.println(bigDecimalB);// result ：-2.13

6. ROUND_HALF_EVEN（ If the first digit of the specified decimal place is an odd number, it will be rounded to the last digit , If it is an even number, the contents after the specified decimal places will be discarded ）
   BigDecimal bigDecimalA = new BigDecimal(“2.113”).setScale(2, BigDecimal.ROUND_HALF_EVEN);

System.out.println(bigDecimalA);// result ：2.11 Although it is an odd number , however 3<5, No carry

BigDecimal bigDecimalB = new BigDecimal(“2.115”).setScale(2, BigDecimal.ROUND_HALF_EVEN);

System.out.println(bigDecimalB);// result ：2.12 Because it is an odd number and conforms to " Five in ", Then carry

This rounding mode is also known as “ Banker's Rounding ”, Mainly used in the United States . Round to the nearest , In two fifths .

If the previous one is odd , Then enter , Otherwise, give up .

8.ROUND_UNNECESSARY（ Assert that the requested operation has exact results , So no rounding is required .）
If this rounding mode is specified for the operation to get accurate results , Throw out ArithmeticException