简单加减乘除计算器

package Base;

import java.util.Scanner;

public class method {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
System.out.println("输入数字，在个字符间加空格");
int a=s.nextInt();
String z=s.next();
int b=s.nextInt();
switch (z){
case "+":
System.out.println(a+"+"+b+"="+add(a,b));
break;
case "-":
System.out.println(a+"-"+b+"="+jian(a,b));
break;
case "":
System.out.println(a+""+b+"="+cheng(a,b));
break;
case "/":
System.out.println(a+"/"+b+"="+chu(a,b));
break;
}
}
public static int add(int a,int b){
return a+b;
}
public static int jian(int a,int b){
return a-b;
}
public static int cheng(int a,int b){
return a*b;
}
public static int chu(int a,int b){
return a/b;
}
}

请输入两个数字与算数符号，各个之间加空格：
4 * 5
4*5=20