double保留两位小数的不同方法：

1.使用BigDecimal类

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);
}

2.DecimalFormat转换最简便

double f = 111231.5585;
public void m2() {
    DecimalFormat df = new DecimalFormat("#.00");
    System.out.println(df.format(f));
}

3.String.format 打印方便

public void m3() {
    System.out.println(String.format("%.2f", f));
}

4.NumberFormat

public void m4() {
        NumberFormat nf = NumberFormat.getNumberInstance();
        nf.setMaximumFractionDigits(2);
        System.out.println(nf.format(f));
}

5.Math

(double)Math.round(0.123*100)/100