Balloon Comes! hdu（小数位数处理）

Balloon Comes!
Time Limit: / MS (Java/Others) Memory Limit: / K (Java/Others)
Total Submission(s):  Accepted Submission(s):   

Problem Description
The contest starts now! How excited it is to see balloons floating around. You, one of the best programmers in HDU, can get a very beautiful balloon if only you have solved the very very very... easy problem.
Give you an operator (+,-,*, / --denoting addition, subtraction, multiplication, division respectively) and two positive integers, your task is to output the result.
Is it very easy?
Come on, guy! PLMM will send you a beautiful Balloon right now!
Good Luck!

Input
Input contains multiple test cases. The first line of the input is a single integer T (<T<) which is the number of test cases. T test cases follow. Each test case contains a char C (+,-,*, /) and two integers A and B(<A,B<).Of course, we all know that A and B are operands and C is an operator. 

Output
For each case, print the operation result. The result should be rounded to  decimal places If and only if it is not an integer.

Sample Input

+
-
*
/   

Sample Output

-

0.50 

package ACM1;

import java.math.RoundingMode;
import java.text.DecimalFormat;
import java.util.Scanner;

public class hdu1 {
    public static void main(String[]args)
    {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();

        for(int i=0;i<n;i++)
        {   

            String a = scanner.next();
            int b = scanner.nextInt();
            int c = scanner.nextInt();
            //double result = (double)b/(double)c;
            if(a.charAt(0)=='+')
                System.out.println((b+c));
            else if(a.charAt(0)=='-')
                System.out.println((b-c));
            else if(a.charAt(0)=='*')
                System.out.println((b*c));
            else
                {
                    if(b%c==0)
                        System.out.println((b/c));
                    else
                    {
                        DecimalFormat dc = new DecimalFormat("0.00");
                        //dc.setMaximumFractionDigits(2);
                        //dc.setGroupingSize(0);
                        //dc.setRoundingMode(RoundingMode.FLOOR);
                        //System.out.println(dc.format(b/(1.0*c)));//我不明白为什么这个样子不对
                        System.out.format("%.2f",(b/(1.0*c)) ).println();//为什么这个样子对

                    }

                }

            }

        }

    }