写一个自动生成对于加减乘除混合运算用Java怎么写

1. 定义运算符和数字范围

首先，我们需要定义运算符和数字的范围。我们可以使用枚举类型来定义运算符，以及使用常量来定义数字的范围。例如：

enum Operator {
    ADD, SUBTRACT, MULTIPLY, DIVIDE
}

public class Calculator {
    private static final int MIN_NUMBER = 0;
    private static final int MAX_NUMBER = 100;
}

2. 随机生成表达式

接下来，我们可以使用随机数生成器来生成表达式。我们可以使用一个方法来获取一个随机的运算符和数字，然后将它们组合成一个表达式。例如：

private static String generateExpression() {
    Random random = new Random();
    int number1 = random.nextInt(MAX_NUMBER - MIN_NUMBER) + MIN_NUMBER;
    int number2 = random.nextInt(MAX_NUMBER - MIN_NUMBER) + MIN_NUMBER;
    Operator operator = Operator.values()[random.nextInt(Operator.values().length)];
    return number1 + " " + operator + " " + number2;
}

3. 计算表达式

最后，我们可以编写一个方法来计算表达式的值。我们可以将表达式拆分成数字和运算符，然后根据运算符执行相应的操作。例如：

private static int calculateExpression(String expression) {
    String[] tokens = expression.split(" ");
    int number1 = Integer.parseInt(tokens[0]);
    int number2 = Integer.parseInt(tokens[2]);
    Operator operator = Operator.valueOf(tokens[1]);
    switch (operator) {
        case ADD:
            return number1 + number2;
        case SUBTRACT:
            return number1 - number2;
        case MULTIPLY:
            return number1 * number2;
        case DIVIDE:
            return number1 / number2;
        default:
            throw new IllegalArgumentException("Invalid operator: " + operator);
    }
}

完整代码如下：

import java.util.Random;

enum Operator {
    ADD, SUBTRACT, MULTIPLY, DIVIDE
}

public class Calculator {
    private static final int MIN_NUMBER = 0;
    private static final int MAX_NUMBER = 100;

    public static void main(String[] args) {
        for (int i = 0; i < 10; i++) {
            String expression = generateExpression();
            int result = calculateExpression(expression);
            System.out.println(expression + " = " + result);
        }
    }

    private static String generateExpression() {
        Random random = new Random();
        int number1 = random.nextInt(MAX_NUMBER - MIN_NUMBER) + MIN_NUMBER;
        int number2 = random.nextInt(MAX_NUMBER - MIN_NUMBER) + MIN_NUMBER;
        Operator operator = Operator.values()[random.nextInt(Operator.values().length)];
        return number1 + " " + operator + " " + number2;
    }

    private static int calculateExpression(String expression) {
        String[] tokens = expression.split(" ");
        int number1 = Integer.parseInt(tokens[0]);
        int number2 = Integer.parseInt(tokens[2]);
        Operator operator = Operator.valueOf(tokens[1]);
        switch (operator) {
            case ADD:
                return number1 + number2;
            case SUBTRACT:
                return number1 - number2;
            case MULTIPLY:
                return number1 * number2;
            case DIVIDE:
                return number1 / number2;
            default:
                throw new IllegalArgumentException("Invalid operator: " + operator);
        }
    }
}