Java 之小数取整

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));

    }

}