java保留两位小数四种函数

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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("0.00");            //建议用0.00格式，#.00或者.00有bug            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();        }    }