Java 输入/输出结果

Question

我是 java se 的新手，我遇到了一些问题。 下面的代码应该是一个计算器。它工作正常但是。要计算输出，扫描仪类的输入应该像这样输入：
1：输入第一个数字 - 按键盘上的 Enter 键
2：输入大小写 +-* 或 / 然后再次在键盘上按 enter
3：输入第二个数字并再次按回车键
4：终于输出了

原来是这样的

计算器

2

-

1

计算为1：

问题是有没有办法把它放在一行中

1.输入两个数字 2-1 - 按键盘上的回车键
2。输出显示为 Calculation: 1

public class Calculator {

    public static void main(String... args) {

        int num1;
        int num2;

        Scanner scan = new Scanner(System.in);
        System.out.println("Calculator");

        num1 = scan.nextInt();
        String str = scan.next();
        num2 = scan.nextInt();

        System.out.print(("Calculation is " + calculate(num1, str, num2)));
        scan.close();

    }

    private static int calculate(int num1, String str, int num2) {

        switch (str.charAt(0)) {
        case '+':
            return num1 + num2;
        case '-':
            return num1 - num2;
        case '*':
            return num1 * num2;
        case '/':
            return num1 / num2;

        }
        return calculate(num1, str, num2);

    }
}

Answer 1

如果您只想将用户的输入显示在一行中，那么您可以轻松实现这一点，而无需更改当前实现中的一行代码。您只需将输入与空格分开即可。

所以不要使用 2-1，而是使用 2 - 1

扫描器使用分隔符模式将其输入分解为标记，默认情况下匹配空格。然后可以使用各种 next 方法将生成的标记转换为不同类型的值... Scanner Java Documentation

希望这会有所帮助！

Answer 2

是的，这是可能的，这样做的方法是使用一个字符串来捕获整个操作，然后将其分解为不同的部分。`public class application {

public static void main(String[] args) {



    // get the operation from the user
    Scanner scan = new  Scanner(System.in);

    System.out.print("Enter your operation : ");

    String operation = scan.nextLine();


    // booleans to evaluate to true if a certain sign is use
    boolean isAddition = operation.contains("+");
    boolean isSubstration = operation.contains("-");
    boolean isDivision = operation.contains("/");
    boolean isMultiplication = operation.contains("*");

    if(isAddition){       
        // get result from the function in charge of processing the operation 
       int result = processOperation(operation, '+');
       //output the result
       System.out.println(" = "+result);
    }
    if(isSubstration){     
       // get result from the function in charge of processing the operation
       int result = processOperation(operation, '-');
       //output the result
       System.out.println(" = "+result);
    }
    if(isDivision){ 
    // get result from the function in charge of processing the operation 
       int result = processOperation(operation, '/');
       //output the result
       System.out.println(" = "+result);
    }
    if(isMultiplication){   
       // get result from the function in charge of processing the operation
       int result = processOperation(operation, '*');
       //output the result
       System.out.println(" = "+result);
    }

}

private static int processOperation(字符串操作，字符符号){

        //remove all the whitespace in the string
        operation = operation.replaceAll("\\s+", "");

        // get the position of the sign operator in the String
        int signIndex = operation.indexOf(sign);

        //get the first number from the string which start from index 0 up to signIndex 
        int num1 = Integer.parseInt(operation.substring(0, signIndex));

        //get the second number from the string which is start from signIndex 
        int num2 = Integer.parseInt(operation.substring(signIndex+1));


        //evaluate the sign in use in order to perfom the appropriate operation 
    if (sign == '+') {
        return num1 + num2;
    } else if (sign == '-') {
        return num1 - num2;
    } else if (sign == '*') {
        return num1 * num2;
    } else {
        return num1 / num2;
    }
}

}`