Java保留小数位的4种方法

import java.math.BigDecimal;  
import java.text.DecimalFormat;  
import java.text.NumberFormat;  
  
public class Format {  
    static double f = 111231.55856666666;  
  
    public static void m1() {  
        BigDecimal bg = new BigDecimal(f);  
        double f1 = bg.setScale(4,BigDecimal.ROUND_HALF_UP).doubleValue();  
        System.out.println(f1);  
    }  
  
    /** 
     * DecimalFormat转换最简便 
     */  
    public static void m2() {  
        DecimalFormat df = new DecimalFormat("#.0000");  
        System.out.println(df.format(f));  
    }  
  
    /** 
     * String.format打印最简便 
     */  
    public static void m3() {  
        System.out.println(String.format("%.4f",f));  
    }  
  
    public static void m4() {  
        NumberFormat nf = NumberFormat.getNumberInstance();  
        nf.setMaximumFractionDigits(4);  
        System.out.println(nf.format(f));  
    }  
  
    public static void main(String[] args) {  
        Format.m1();  
        Format.m2();  
        Format.m3();  
        Format.m4();  
    }  
}