转自： http://blog.csdn.net/ming1683/article/details/3195058

4种方法，都是四舍五入，例：

import java.math.BigDecimal;
import java.text.DecimalFormat;
import java.text.NumberFormat;
public class format {double f = 111231.5585;public void m1() {BigDecimal bg = new BigDecimal(f);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(f));}/*** String.format打印最简便*/public void m3() {System.out.println(String.format("%.2f", f));}public void m4() {NumberFormat nf = NumberFormat.getNumberInstance();nf.setMaximumFractionDigits(2);System.out.println(nf.format(f));}public static void main(String[] args) {format f = new format();f.m1();f.m2();f.m3();f.m4();}
}

结果：
111231.56
111231.56
111231.56
111,231.56