java保留两位小数四种方法

package com.echo;
import java.math.BigDecimal;
import java.text.DecimalFormat;
import java.text.NumberFormat;
/**
 * Java保留两位小数四种方法
 * 
 * @author Echo
 *
 */
public class RetainTwoDecimal {
        double retainTwoDecimal = 111231.5585;
        public void m1() {
                BigDecimal bg = new BigDecimal(retainTwoDecimal);
                double f1 = bg.setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue();
                System.out.println(f1);
        }
        /**
         * DecimalFormat转换最简便
         */
        public void m2() {
                DecimalFormat df = new DecimalFormat("#.00");
                System.out.println(df.format(retainTwoDecimal));
        }
        /**
         * String.format打印最简便
         */
        public void m3() {
                System.out.println(String.format("%.2f", retainTwoDecimal));
        }
        public void m4() {
                NumberFormat nf = NumberFormat.getNumberInstance();
                nf.setMaximumFractionDigits(2);
                System.out.println(nf.format(retainTwoDecimal));
        }
        public static void main(String[] args) {
                RetainTwoDecimal retainTwoDecimal = new RetainTwoDecimal();
                retainTwoDecimal.m1();
                retainTwoDecimal.m2();
                retainTwoDecimal.m3();
                retainTwoDecimal.m4();
        }
}