JAVA学习：方法

/*
 * 方法
 */
public class Calc {
    
    //方法标识符要注意：static 以及方法的类型 double
    public static double add(double a , double b){
        double r = a+b;
        return r;
    }
    
    public static double sub(double a , double b){
        double r = a - b;
        return r;
    }
    
    public static double mul(double a , double b){
        double r = a * b;
        return r;
    }
    
    public static double div(double a , double b){
        double r = a / b;
        return r;
    }

}

import java.util.Scanner;
public class TestCalc 
    public static void main(String args[]) {
        
        //接受数据
        Scanner sc = new Scanner(System.in);
        System.out.println("num1:");
        double num1 = sc.nextDouble();
        
        //接受操作符
        System.out.println("opp:");
        String opp = sc.next();
        //char opp1 = opp.charAt(index);
        System.out.println("num2");
        double num2 = sc.nextDouble();
        double d = 0;
        
        //调用相应的业务逻辑
        switch(opp)){
            //注意:在 JDK7 版本之前 switch 语句不支持String 类型做参数。
            case "+" :
                d = Calc.add(num1,num2);
                break;
            case "-" :
                d = Calc.sub(num1,num2);
                break;
            case "*" :
                d = Calc.mul(num1,num2);
                break;
                
            case "/" :
                d = Calc.div(num1,num2);
                break;
            default :
                System.out.println("ErrorMessage!");
                break;
        }
    }
}