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();

    }

}