java 代码保留小数位方法

import java.math.BigDecimal;
import java.text.DecimalFormat;
import java.text.NumberFormat;

public class format {
double f = 1259846789;
public void m1(){
BigDecimal bg = new BigDecimal(f);//浮点数超过Double类型可用BigDecimal表示范围
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();

}

}