java中实现四舍五入的4种方法

public static void main(String[] args) {    // 实现四舍五入    double d=4.015;    //d=7.485;    //方法一    DecimalFormat df=new DecimalFormat("#.00");    df.setRoundingMode(RoundingMode.HALF_UP);    System.out.println(df.format(d));    //方法二    System.out.println(new BigDecimal(d+"").setScale(2,BigDecimal.ROUND_HALF_UP).toString());    //方法三    System.out.println(String.format("%.2f", d));    //方法四    NumberFormat nf = NumberFormat.getNumberInstance();    nf.setMaximumFractionDigits(2);    nf.setRoundingMode(RoundingMode.HALF_UP);        System.out.println(nf.format(d));}