Re-learning Java (2): Processing of Java numbers

A simple example

1      Public void Testnum () {2         System.out.println (Math.Round (12.5)); 3         System.out.println (Math.Round ( -12.5)); 4     }56     output:137             -12

The output is determined by theThe rounding rules of the math.round affect.

TwoRounding method in Java

 1.round_up: Rounding away from 0 directions. Rounding in the direction of the absolute maximum, as long as the bit is discarded0 is rounding.

 2.round_down: tends to round in 0 direction. Enter in the direction of the smallest absolute value, all the bits are discarded, there is no rounding.

 3.round_ceiling: Rounds to positive infinity. To the positive maximum direction. If positive, the rounding behavior is similar toROUND_UP, if negative, rounding behavior
Similar toRound_down.The Math.Round () method is the use of this pattern.

 4.round_floor: Rounds to negative infinity. To the negative Infinity direction. If positive, the rounding behavior is similar toRound_down; If negative, rounding behavior
Similar toround_up. 
 
 5.HALF_UP: Recent number rounding  (5 in ). This is our most classic rounding. 
 
 6.half_down: Recent number rounding  (5 Span style= "font-family: ' Consolas ';" >). Here 5 is to be discarded. 
 
 7.hail_even: Banker Rounding Method. The value of the shed bit is less than 5 when directly shed, greater than  5 o'clock carry back, equals 5 when there are other non-0 value is rounded up 
, if 5 is followed by Span style= "font-family: ' Consolas ';" >0 is based on 5 in front of the number of parity judgments, odd-numbered, even-numbered homes. 
 
 Banker Algorithm Example: 
               

1  Public Static voidMain (string[] args) {2BigDecimal d =NewBigDecimal (100000);//Deposit3BigDecimal r =NewBigDecimal (0.001865*3);//Interest4BigDecimal i = d.multiply (R). Setscale (2,roundingmode.half_even);//using the Banker algorithm5 6SYSTEM.OUT.PRINTLN ("Quarterly interest is:" +i);7                 }8 Output:9Quarterly interest is: 559.50

< Span style= "font-family: ' Consolas ';" >< Span style= "font-family: ' Consolas ';" > 
 Span style= "font-family: ' Consolas ';" > 
 Three, set precision 
 
  BigDecimal 
               

1  Public void Testnumberscale () {2             double d = 123456.7850; 3             New BigDecimal (d); 4             double D1 = Bigdecimal.setscale (2, bigdecimal.round_half_up). Doublevalue (); 5             System.out.println (D1); 6         }

< Span style= "font-family: ' Consolas ';" >< Span style= "font-family: ' Consolas ';" > here use bigdecimal use setscale set precision, use  ROUND_HALF_UP set rounding rules. 
 
 decimalformat 
 Span style= "font-family: ' Consolas ';" > 
                 

 1  public  void   TestNumberScale2 () { 2  double  d = 123456.7850;  3  decimalformat decimalformat = new  DecimalFormat ("##.00"  4  String d1 = Decimalformat.format (d); 5   System.out.println (D1);  6 } 

< Span style= "font-family: ' Consolas ';" >< Span style= "font-family: ' Consolas ';" >< Span style= "font-family: ' Consolas ';" > 
 string.format 
  
                 

 1  public  void   TestNumberScale3 () { 2  double  d = 123456.7850;  3  String d1 = String.Format ("%.2f" ,d); 4   System.out.println (D1);  5 } 

< Span style= "font-family: ' Consolas ';" >< Span style= "font-family: ' Consolas ';" > 
 < Br> note decimalformat rounding rules and 3 different 
               

Re-learn Java (2): Handling of Java numbers