BigDecimal the best way to preserve the decimal point in Java __java

[Original]bigdecimal Java, the best way to keep the decimal point

2014-3-31 Reading 332 Comments 0 Java, there are four ways to keep the decimal places, as follows:

<span style= "padding:0px; margin:0px; font-family: ' Microsoft Yahei '; font-size:14px; "
>import Java.math.BigDecimal;
Import Java.text.DecimalFormat;
Import Java.text.NumberFormat;
        public class Format {Double f = 231.52;//0.9,2 public void M1 () {BigDecimal bg = new BigDecimal (f);
        Double f1 = Bg.setscale (2, bigdecimal.round_half_up). Doublevalue ();
    System.out.println (F1);
        /** * DecimalFormat Conversion is easiest/public void m2 () {DecimalFormat df = new DecimalFormat ("#.00");
    System.out.println (Df.format (f));
    /** * String.Format Print easiest/public void m3 () {System.out.println (String.Format ("%.2f", f));
        public void M4 () {NumberFormat NF = numberformat.getnumberinstance ();
        Nf.setmaximumfractiondigits (2);
    System.out.println (Nf.format (f));
        public static void Main (string[] args) {format f = new format ();
        F.M1 ();
       F.M2 (); F.M3 ();
    F.M4 (); }}</span>

But as on, for integers and decimal fraction m2,m3,m4 These three methods have a problem, so it is best to use the M1 BigDecimal, introduced as follows:

The Bigdecimal.setscale () method is used to format the decimal point
Setscale (1) means to keep a decimal number by default by rounding
Setscale (1,bigdecimal.round_down) directly remove the extra decimal places, such as 2.35 will become 2.3
Setscale (1,BIGDECIMAL.ROUND_UP) carry handle, 2.35 becomes 2.4
Setscale (1,bigdecimal.round_half_up) rounded, 2.35 turned 2.4

Setscaler (1,bigdecimal.round_half_down) rounded, 2.35 becomes 2.3, if 5 is down-shed

Setscaler (1,bigdecimal.round_ceiling) close to rounding of positive infinity

Setscaler (1,bigdecimal.round_floor) is close to the rounding of the negative infinity, and the digital >0 is the same as the round_up, the number <0 and the Round_down function

Setscaler (1,bigdecimal.round_half_even) is rounded to the nearest number, and if the distance from two adjacent digits is equal, it is rounded to the adjacent even number.
Note: 1:scale refers to the number of digits after your decimal point. For example, 123.456 score is 3 score () is the method in the BigDecimal class.
For example: BigDecimal B = new BigDecimal ("123.456"); B.scale (), the return is 3.
2:roundingmode is a retention pattern for decimals. They are all constant fields in BigDecimal, and there are many kinds.
For example: BIGDECIMAL.ROUND_HALF_UP says is 4 homes 5.
3:pubilc BigDecimal Divide (BigDecimal divisor, int scale, int roundingmode)
I use a BigDecimal object divided by the result of divisor, and I want this result to keep a scale decimal place, roundingmode means what the retention mode is, rounded or otherwise, you can choose for yourself.

4: For the general Add, subtract, multiply method of decimal format is as follows: BigDecimal mdata = new BigDecimal ("9.655"). Setscale (2, Bigdecimal.round_half _UP);
System.out.println ("mdata=" + mdata); ----Results:-----mdata=9.66