Operation method for BigDecimal in Java

This article illustrates the operation of BigDecimal in Java. Share with you for your reference. Specific analysis is as follows:

BigDecimal is used for business calculations because double, float, and float are not precise enough. The BigDecimal object is created as follows:

BigDecimal b = new BigDecimal("12.000001");

System.out.println(b);

The output result is: 12.000001;

BigDecimal can pass in a String and a double when it's created, but it's best to use a String, as you can see from the following code:

BigDecimal b = new BigDecimal("12.000001");

System.out.println(b);

BigDecimal c = new BigDecimal(12.01);

System.out.println(c);

The running result is:

12.000001
12.0099999999999997868371792719699442386627197265625

You can see that the precision is lost when a double is passed in.

Other operations of BigDecimal are as follows:

    //Add < br / >
    public static BigDecimal add(String num1, String num2) {

        BigDecimal bd1 = new BigDecimal(num1);

        BigDecimal bd2 = new BigDecimal(num2);

        return bd1.add(bd2);

    }

 

    //Subtraction < br / >
    public static BigDecimal subtract(String num1, String num2) {

        BigDecimal bd1 = new BigDecimal(num1);

        BigDecimal bd2 = new BigDecimal(num2);

        return bd1.subtract(bd2);

    }

 

    //Multiplication < br / >
    public static BigDecimal multiply(String num1, String num2) {

        BigDecimal bd1 = new BigDecimal(num1);

        BigDecimal bd2 = new BigDecimal(num2);

        return bd1.multiply(bd2);

    }

 

    //Division < br / >
    public static BigDecimal divide(String num1, String num2, int i) {

        BigDecimal bd1 = new BigDecimal(num1);

        BigDecimal bd2 = new BigDecimal(num2);

        //I is the number of digits to be reserved, and BigDecimal.ROUND_HALF_UP is the rule for rounding 

        return bd1.divide(bd2, i, BigDecimal.ROUND_HALF_DOWN);  

    }

Just to emphasize division, the third parameter is whether to round,

ROUND_HALF_DOWN means when 5 does not enter 1, that is, 1.5-> 1;
ROUND_HALF_UP represents 1 in 5, i.e. 1.5-> 2;

But here's the catch:
When we use ROUND_HALF_DOWN

System.out.println(this.divide("67.75", "5",4));

System.out.println(this.divide("67.75", "5",1));

System.out.println("-------");

System.out.println(this.divide("67.751", "5",4));

System.out.println(this.divide("67.751", "5",1));

The operation results are as follows:

13.5500
13.5
-------
13.5502
13.6

I wonder, the second result is supposed to be 13.5! Why 13.6. Later, after many tests, thought for a moment, the round is not in accordance with the precision behind the shift and 5, but according to the precision of a 5, after all of the data and that is: accurate to 13.5500 a, compared with 5, use 0.0500 and accurate to 13.5502 a, compared with 5, use 0.0502 is greater than 5, so I closed up.

I hope this article has been helpful to your Java programming.