<<= 运算符在 Java 中是什么意思? [英] What does <<= operator mean in Java?

问题描述

您能否解释一下来自 HashMap 构造函数 特别是这一行

Can you please explain this code snippet from HashMap constructor specifically the line

容量<<= 1:

capacity <<= 1:

// Find a power of 2 >= initialCapacity
198         int capacity = 1;
199         while (capacity < initialCapacity)
200             capacity <<= 1;

推荐答案

相当于capacity = capacity <<<1;.
该操作将容量的位向左移动一位，相当于乘以 2.

It is equivalent to capacity = capacity << 1;.
That operation shifts capacity's bits one position to the left, which is equivalent to multiplying by 2.

您发布的特定代码找到大于 initialCapacity 的 2 的最小幂.

The specific code you posted finds the smallest power of 2 which is larger than initialCapacity.

所以如果 initialCapacity 为 27，例如 capacity 在循环后将是 32 (2^5).

So if initialCapacity is 27, for example, capacity will be 32 (2^5) after the loop.

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