java取整和java四舍五入方法，

java取整和java四舍五入方法，

转自http://blog.csdn.net/kankan_summer/article/details/5744576

文章出自http://www.cujava.com

import java.math.BigDecimal;  
import java.text.DecimalFormat;  
public class TestGetInt{  
  public static void main(String[] args){  
    double i=2, j=2.1, k=2.5, m=2.9;  
    System.out.println("舍掉小数取整:Math.floor(2)=" + (int)Math.floor(i));  
    System.out.println("舍掉小数取整:Math.floor(2.1)=" + (int)Math.floor(j));  
    System.out.println("舍掉小数取整:Math.floor(2.5)=" + (int)Math.floor(k));  
    System.out.println("舍掉小数取整:Math.floor(2.9)=" + (int)Math.floor(m));  
                                                                                 
    /* 这段被注释的代码不能正确的实现四舍五入取整 
    System.out.println("四舍五入取整:Math.rint(2)=" + (int)Math.rint(i)); 
    System.out.println("四舍五入取整:Math.rint(2.1)=" + (int)Math.rint(j)); 
    System.out.println("四舍五入取整:Math.rint(2.5)=" + (int)Math.rint(k)); 
    System.out.println("四舍五入取整:Math.rint(2.9)=" + (int)Math.rint(m)); 
    
    System.out.println("四舍五入取整:(2)=" + new DecimalFormat("0").format(i)); 
    System.out.println("四舍五入取整:(2.1)=" + new DecimalFormat("0").format(i)); 
    System.out.println("四舍五入取整:(2.5)=" + new DecimalFormat("0").format(i)); 
    System.out.println("四舍五入取整:(2.9)=" + new DecimalFormat("0").format(i)); 
    */  
     
    System.out.println("四舍五入取整:(2)=" + new BigDecimal("2").setScale(0, BigDecimal.ROUND_HALF_UP));  
    System.out.println("四舍五入取整:(2.1)=" + new BigDecimal("2.1").setScale(0, BigDecimal.ROUND_HALF_UP));  
    System.out.println("四舍五入取整:(2.5)=" + new BigDecimal("2.5").setScale(0, BigDecimal.ROUND_HALF_UP));  
    System.out.println("四舍五入取整:(2.9)=" + new BigDecimal("2.9").setScale(0, BigDecimal.ROUND_HALF_UP));  
    System.out.println("凑整:Math.ceil(2)=" + (int)Math.ceil(i));  
    System.out.println("凑整:Math.ceil(2.1)=" + (int)Math.ceil(j));  
    System.out.println("凑整:Math.ceil(2.5)=" + (int)Math.ceil(k));  
    System.out.println("凑整:Math.ceil(2.9)=" + (int)Math.ceil(m));  
    System.out.println("舍掉小数取整:Math.floor(-2)=" + (int)Math.floor(-i));  
    System.out.println("舍掉小数取整:Math.floor(-2.1)=" + (int)Math.floor(-j));  
    System.out.println("舍掉小数取整:Math.floor(-2.5)=" + (int)Math.floor(-k));  
    System.out.println("舍掉小数取整:Math.floor(-2.9)=" + (int)Math.floor(-m));  
     
    System.out.println("四舍五入取整:(-2)=" + new BigDecimal("-2").setScale(0, BigDecimal.ROUND_HALF_UP));  
    System.out.println("四舍五入取整:(-2.1)=" + new BigDecimal("-2.1").setScale(0, BigDecimal.ROUND_HALF_UP));  
    System.out.println("四舍五入取整:(-2.5)=" + new BigDecimal("-2.5").setScale(0, BigDecimal.ROUND_HALF_UP));  
    System.out.println("四舍五入取整:(-2.9)=" + new BigDecimal("-2.9").setScale(0, BigDecimal.ROUND_HALF_UP));  
    System.out.println("凑整:Math.ceil(-2)=" + (int)Math.ceil(-i));  
    System.out.println("凑整:Math.ceil(-2.1)=" + (int)Math.ceil(-j));  
    System.out.println("凑整:Math.ceil(-2.5)=" + (int)Math.ceil(-k));  
    System.out.println("凑整:Math.ceil(-2.9)=" + (int)Math.ceil(-m));  
    }  
}  
  
/* Output: 
舍掉小数取整:Math.floor(2)=2 
舍掉小数取整:Math.floor(2.1)=2 
舍掉小数取整:Math.floor(2.5)=2 
舍掉小数取整:Math.floor(2.9)=2 
四舍五入取整:(2)=2 
四舍五入取整:(2.1)=2 
四舍五入取整:(2.5)=3 
四舍五入取整:(2.9)=3 
凑整:Math.ceil(2)=2 
凑整:Math.ceil(2.1)=3 
凑整:Math.ceil(2.5)=3 
凑整:Math.ceil(2.9)=3 
舍掉小数取整:Math.floor(-2)=-2 
舍掉小数取整:Math.floor(-2.1)=-3 
舍掉小数取整:Math.floor(-2.5)=-3 
舍掉小数取整:Math.floor(-2.9)=-3 
四舍五入取整:(-2)=-2 
四舍五入取整:(-2.1)=-2 
四舍五入取整:(-2.5)=-3 
四舍五入取整:(-2.9)=-3 
凑整:Math.ceil(-2)=-2 
凑整:Math.ceil(-2.1)=-2 
凑整:Math.ceil(-2.5)=-2 
凑整:Math.ceil(-2.9)=-2 
*///:~