java - 为什么这会返回错误的模数答案？

Question

这个问题已经有答案了:

Best way to make Java's modulus behave like it should with negative numbers? (7 个回答)

已关闭 9 年前。

    private int mCurrentIndex = 0;
    mPrevButton = (Button)findViewById(R.id.prev_button);
    mPrevButton.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            mCurrentIndex = (-33 % 5);
            Log.i("IndexClick", String.valueOf(mCurrentIndex));
        }
    });

这将返回 -3 而不是 2。它用正数进行正确的数学运算。请帮助似乎无法找到解决方案。

Answer 1

根据 JLS, Section 15.17.3，使用 % 运算符时，余数的符号必须与被除数的符号匹配(或者为 0)。 :

The remainder operation for operands that are integers after binary numeric promotion (§5.6.2) produces a result value such that (a/b)*b+(a%b) is equal to a.

It follows from this rule that the result of the remainder operation can be negative only if the dividend is negative, and can be positive only if the dividend is positive. Moreover, the magnitude of the result is always less than the magnitude of the divisor.

事实上，(-33/5)*5 + (-33%5) 变为 -6*5 + (-3) ，等于 -33.

要获得积极的结果，您必须获得积极的股息。