double f = 111231.5585;
System.out.println(String.format("%.2f", f));

double f = 111231.5585;
DecimalFormat df = new DecimalFormat("#.00");            
System.out.println(df.format(f));

double f = 111231.5585;
BigDecimal bg = new BigDecimal(f);            
double f1 = bg.setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue();            
System.out.println(f1);

double f = 111231.5585;
NumberFormat nf = NumberFormat.getNumberInstance();            
nf.setMaximumFractionDigits(2);            
System.out.println(nf.format(f));

 1 import java.math.BigDecimal; 
 2     import java.text.DecimalFormat; 
 3     import java.text.NumberFormat; 
 4     public class format { 
 5         double f = 111231.5585; 
 6         public void m1() { 
 7             BigDecimal bg = new BigDecimal(f); 
 8             double f1 = bg.setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue(); 
 9             System.out.println(f1);
 10         }
 11         /**
 12          * DecimalFormat转换最简便
 13          */
 14         public void m2() {
 15             DecimalFormat df = new DecimalFormat("#.00");
 16             System.out.println(df.format(f));
 17         }
 18         /**1
 9          * String.format打印最简便
 20          */
 21         public void m3() {
 22             System.out.println(String.format("%.2f", f));
 23         }
 24         public void m4() {
 25             NumberFormat nf = NumberFormat.getNumberInstance();
 26             nf.setMaximumFractionDigits(2);
 27             System.out.println(nf.format(f));
 28         }
 29         public static void main(String[] args) {
 30             format f = new format();
 31             f.m1();
 32             f.m2();
 33             f.m3();
 34             f.m4();
 35         }
 36     }