java - 为什么数字在 HashMap.java 类中被硬编码为 1<<4

Question

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Answer 1

这是为了强调它们是 2 的幂，必须是 2 的幂并且是写 2 的幂的一种简单方法。

来自 Java 8 的源代码:

/**
 * The default initial capacity - MUST be a power of two.
 */
static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16

/**
 * The maximum capacity, used if a higher value is implicitly specified
 * by either of the constructors with arguments.
 * MUST be a power of two <= 1<<30.
 */
static final int MAXIMUM_CAPACITY = 1 << 30;