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));
}