后缀表达式求值器中Math.pow未正确计算幂运算，返回乘积结果？

Hey there, let's break down this problem you're having with your postfix calculator—this exact issue has tripped up a few folks I've helped before, so I think I know where to look.

The key clue here is that only num^num gives the right result, while any other exponent operation spits out a product instead. That makes perfect sense because when both numbers are the same, their product equals their power (like 2*2=2²=4), so it looks like it's working. But for different numbers, you're getting multiplication instead of exponentiation—so let's dig into why that's happening.

First off, let's look at the most likely culprits:

1. You accidentally used multiplication instead of Math.pow() in your ^ case #

This is super common, especially if you copied the logic from the * operator case and forgot to update it. Double-check your case "^" block—if you see something like result = a * b; instead of calling Math.pow(), that's your problem right there.

Fix it by making sure you're actually invoking Math.pow(), and pay attention to the order of your operands:

case "^": {
    // Remember: in postfix, the top of the stack is the RIGHT operand
    double exponent = stack.pop();
    double base = stack.pop();
    result = (int) Math.pow(base, exponent); // Calculate base^exponent
    stack.push(result);
    break;
}

2. You popped the stack in the wrong order #

Postfix notation works by pushing operands onto the stack, then popping the right operand first when you hit an operator. For example, if your input is 3 2 ^, that means "3 raised to the power of 2". So you need to pop 2 (the exponent) first, then 3 (the base), then pass them to Math.pow(base, exponent).

While popping in reverse order won't give you a product, it will give you the wrong power result (like 2³ instead of 3²), so it's still a common mistake worth checking if the first fix doesn't solve things.

3. Quick debug tip to confirm what's happening #

Add simple print statements to your ^ case to see exactly what operands are being used and what Math.pow() is returning:

case "^": {
    double exponent = stack.pop();
    double base = stack.pop();
    System.out.println("Calculating " + base + " ^ " + exponent);
    double powResult = Math.pow(base, exponent);
    System.out.println("Power result: " + powResult);
    result = (int) powResult;
    System.out.println("Casted to int: " + result);
    stack.push(result);
    break;
}

This will immediately show you if the operands match what you expect, and whether Math.pow() is actually doing its job.

内容的提问来源于stack exchange，提问作者Brenton K