在Java如何计算结果？[副本]

Question

我创建这段代码是为了创建随机数和运算符，但它如何计算并显示结果呢？

它现在做的是，例如打印出来:4+1-3或9*2-8等。我不知道如何计算出4+1-3或9*2-8的结果，然后打印出来。

public static void main(String[] args) {
    int t = 0;
    String[] operators = {"-", "+", "*"};
    String operator;
    Random r = new Random();

    for (int i = 0; i < 3; i++) {
        int randNum = randNums(9, 1);
        operator = operators[r.nextInt(operators.length)];
        System.out.print(randNum);
        if (t < 2) {
            System.out.print(operator);
            t++;
        }
    }

}

Answer 1

这是一些（相对）简单的代码，将从左到右计算表达式（它没有考虑到操作的顺序，因此3+4*5的计算结果为(3+4)*5，而不是正确的3+(4*5)):

public static void main(String[] args) {
    String[] operators = {"-", "+", "*"};
    String operator;
    Random r = new Random();
    int result = -1;

    for (int i = 0; i < 3; i++) {
        int randNum = r.nextInt(9) + 1; // 1 - 9 inclusive
        if (i != 0) {
            operator = operators[r.nextInt(operators.length)];
            System.out.print(operator);
            result = calculate(result, randNum, operator);
        }
        else {
            result = randNum;
        }
        System.out.print(randNum);
    }
    System.out.println("=" + result);
}
public static int calculate(int operand1, int operand2, String operator) {
    switch (operator) {
        case "+":
            return operand1 + operand2;
        case "-":
            return operand1 - operand2;
        case "*":
            return operand1 * operand2;
        default:
            throw new RuntimeException();
    }
}