关于java中用switch语句实现计算器的运算问题，为什么运算符opr的初始值为'/'?

import java.util.Scanner;

public class MiniCal {

public static void main(String[] args) {
char opr = '/';
Scanner input = new Scanner(System.in);
System.out.print("请输入第一个操作数: ");
int data1 = input.nextInt();
System.out.print("请输入第二个操作数：");
int data2 = input.nextInt();
int result = 0;

switch (opr) {
case '+':
result = data1 + data2;
break;
case '-':
result = data1 - data2;
break;
case '*':
result = data1 * data2;
break;
case '/':
result = data1 / data2;
break;
}

System.out.println(data1 + " " + opr + " " + data2 + " = " + result);
}
}