java - 如何从数组中选择一个值？

Question

如何从数组中选择一个值？示例是这个 String[] ans = {"+", "-", "/", "*"}; 然后我想选择 "+"。

public static void main(String[] args) {
    String[] ans = {"+","-","/","*"};
    Random random = new Random();
    Scanner calcu = new Scanner(System.in);
    System.out.print("Enter First number: ");
    numOne = calcu.nextInt();
    System.out.print("Enter Second number: ");
    numTwo = calcu.nextInt();
    System.out.print("Choose an Operator to use");

}

Answer 1

您可以使用 ans[0] 作为“+”等等。

ans[0] = "+";
ans[1] = "-";
ans[2] = "/";
ans[3] ="*";

在您的情况下，此代码将帮助您:

     public static void main(String[] a) {

        String[] ans = {"+","-","/","*"};
        double result = 0;
        Scanner calcu = new Scanner(System.in);
        System.out.print("Enter First number: ");
        int numOne = calcu.nextInt();
        System.out.print("Enter Second number: ");
        int numTwo = calcu.nextInt();
        System.out.print("Choose an Operator to use");
        String oparation= calcu.next();

        if(oparation.equals(ans[0])){
           result = numOne + numTwo;
        }
        else if(oparation.equals(ans[1])){
            result = numOne - numTwo;
        }
        else if(oparation.equals(ans[2])){
            result = numOne / numTwo;

        } else if(oparation.equals(ans[3])){
            result = numOne * numTwo;
        }
        System.out.println("result is " + result);

   }

如果您希望使用 switch 语句获得相同的结果:

public static void main(String[] a) {

        double result = 0;
        Scanner calcu = new Scanner(System.in);
        System.out.print("Enter First number: ");
        int numOne = calcu.nextInt();
        System.out.print("Enter Second number: ");
        int numTwo = calcu.nextInt();
        System.out.print("Choose an Operator to use");
        String oparation= calcu.next();

        switch(oparation){
            case "+" :
            result = numOne + numTwo;
            break;

            case "-" :
            result = numOne - numTwo;
            break;

            case "/" :
            result = numOne / numTwo;
            break;

            case "*" :
            result = numOne * numTwo;
            break;
        }
        System.out.println("result is " + result);

   }

但是，使用 switch 语句，如果您想比较 case ans[0]: 而不是 case "*"，那么你可以使用 enum。