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();
	}
}