Java 第一次尝试简单的计算器（发生了什么？）

Question

Main.java（主要Class）

package com.indie;

import java.util.InputMismatchException;
import java.util.Scanner;

import static com.indie.Operations.*;

public class Main {
    private static double Number1;
    private static double Number2;
    private static double Total;
    private static String Symbol;
    private static boolean noError;
    private static boolean exceptioncaught;
    public static void main(String[] args) throws InterruptedException{
        noError = false;
        while (!noError) {
            exceptioncaught = false;
            while (!exceptioncaught) {
                Scanner scanner = new Scanner(System.in);
                System.out.println("Enter your number:");
                try {
                    Number1 = scanner.nextDouble();
                } catch (InputMismatchException ex) {
                    System.out.println();
                    System.out.println("TypeERROR: You didn't input a vaild number!");
                    exceptioncaught = true;
                    System.out.println();
                    Thread.sleep(3000);
                    break;
                }
             System.out.println("What do you want to do:");
            Symbol = scanner.next();
            if (!Symbol.contains("+") && !Symbol.contains("-") && !Symbol.contains("*") && !Symbol.contains("x") && !Symbol.contains("/") && !Symbol.contains("÷")) {
                System.out.println();
                System.out.println("TypeERROR: You didn't input a valid symbol!");
                exceptioncaught = true;
                System.out.println();
                Thread.sleep(3000);
                break;
                }
                System.out.println("Enter your second number:");
                try {
                    Number1 = scanner.nextDouble();
                } catch (InputMismatchException ex) {
                    System.out.println();
                    System.out.println("TypeERROR: You didn't input a vaild number!");
                    exceptioncaught = true;
                    System.out.println();
                    Thread.sleep(3000);
                    break;
                }
                System.out.println();
                if (Symbol.contains("+")) {
                    Total = Add(Number1, Number2);
                    noError = true;
                    break;
                } else if (Symbol.contains("-")) {
                    Total = Subtract(Number1, Number2);
                    noError = true;
                    break;
                } else if (Symbol.contains("*") || Symbol.contains("x")) {
                    Total = Multiply(Number1, Number2);
                    noError = true;
                    break;
                } else if (Symbol.contains("/") || Symbol.contains("÷")) {
                    Total = Divide(Number1, Number2);
                    noError = true;
                    break;
                }
            }
        }
        System.out.println(String.valueOf(Number1)
                           +Symbol+String.valueOf(Number2) 
                           +"="+String.valueOf(Total));
    }
}

Operations.java（第二个Class）

package com.indie;

public class Operations {
    public static double Add(double x, double y) { return x+y; }
    public static double Subtract(double x, double y){ return x-y; }
    public static double Multiply(double x, double y){ return x*y; }
    public static double Divide(double x, double y){ return x/y; }
}

Got this result

有什么办法可以解决吗？怎么会变成2.0+20.0=2.0呢？请帮忙。有什么方法可以防止它给出那种类型的结果？

Other results:

result 1:

Enter your number:

2

What do you want to do:

+5

Enter your second number:

56

56.0+50.0=56.0

result 2:

Enter your number:

1

What do you want to do:

+1

Enter your second number:

1

1.0+10.0=1.0

Answer 1

在这部分代码中，您应该更改为：

...
System.out.println("Enter your second number:");
try {
    Number1 = scanner.nextDouble();
}
...

对此：

...
System.out.println("Enter your second number:");
try {
    Number2 = scanner.nextDouble();
}
...

您永远不会在代码中更改 Number2 的值。

Answer 2

多一双眼睛真好在您的代码中，您永远不会为 Number 2

赋值

System.out.println("Enter your second number:");
try {
     Number2 = scanner.nextDouble();

Java 第一次尝试简单的计算器（发生了什么？）

Java first attempt on simple calculator (what's happened?)

java

console

calculator