일하면서 기록하기

사칙연산하기

package switch_Ex;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.text.DecimalFormat;

public class SwitchTeat02_1 {
	public static void main(String[] args) throws IOException{
		DecimalFormat df = new DecimalFormat("#.###");
		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int a, b;
		String op;
		
		System.out.println("2개의 정수형 숫자와 연산자(+,-,*,/)를 입력하여 계산하시오");
		System.out.print("a 입력 : ");
		a = Integer.parseInt(br.readLine());
		System.out.print("b 입력 : ");
		b = Integer.parseInt(br.readLine());
		System.out.print("연산자(+,-,*,/) 입력 : ");
		op = br.readLine();
		
		double result =0;
		switch(op) {
		case "+" : result = a + b; break;
		case "-" : result = a - b; break;
		case "*" : result = a * b; break;
		case "/" : result = (double)a / b; break;
		default : System.out.println("연산자 error");
		  		  System.exit(0);//문장을 그냥 끝내는 코드
		 
		}
		System.out.println(a+op+b+" = "+df.format(result));
		
	}

}

다른방법

package switch_Ex;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class SwitchTest02 {
	public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int a, b, result;
		String op;
		
		System.out.println("2개의 정수형 숫자와 연산자(+,-,*,/)를 입력하여 계산하시오");
		System.out.print("a 입력 : ");
		a = Integer.parseInt(br.readLine());
		System.out.print("b 입력 : ");
		b = Integer.parseInt(br.readLine());
		System.out.print("연산자(+,-,*,/) 입력 : ");
		op = br.readLine();
		
		
		switch(op) {
		case "+" : System.out.println(a+" + "+b+" = "+(a+b));
					break;
		case "-" : System.out.println(a+" - "+b+" = "+(a-b));
					break;
		case "*" : System.out.println(a+" * "+b+" = "+(a*b));
					break;
		case "/" : System.out.println(a+" / "+b+" = "+String.format("%.3f", ((double)a/b)));
					break;
		default : System.out.println("연산자 error");
		}
		
	}

}