java - 在我输入数学运算的运算符之前程序终止

Question

正如标题所说，程序在数学运算符的用户输入可以输入之前终止，并立即向运算符输出无效输入的错误消息，即使从未输入过。

代码如下：

导入 java.util.Scanner；// 用户输入扫描器

公共类 asg2{

公共静态无效主要（字符串[]参数）{

Scanner scan = new Scanner(System.in);


System.out.println("Please, enter any two numbers separated by a space: ");
    double Input = scan.nextDouble();
    double Input2 = scan.nextDouble();

System.out.println("Next, please enter the mathematical operation symbol you wish these numbers to have performed on them: ");
    String Math = scan.nextLine();
    
double In1 = Input;
double In2 = Input2;
double out = 0;

    if (Math.equals("*")) {
    out = (In1 * In2);
    System.out.print("Evaluation: " +In1+ " * " +In2+" = " +out);
    }

    if (Math.equals("/")) {
    out = (In1 / In2);
    System.out.print("Evaluation: " +In1+ " / " +In2+" = " +out);
    }

    if (Math.equals("+")) {
    out = (In1 + In2);
    System.out.print("Evaluation: " +In1+ " + " +In2+" = " +out);
    }

    if (Math.equals("-")) {
    out = (In1 - In2);
    System.out.print("Evaluation: " +In1+ " - " +In2+" = " +out);
    }

    if (Math != ("*") || Math != ("-") || Math != ("/") || Math != ("+")) { 
    System.out.print("Evaluation: INVALID OPERATION SYMBOL");
    }
    
    
    

}

}

标签： javamath