Why Does Java's Integer Class Cache Integers from -128 to 127?

Understanding Integer Caching: Range and Rationale

Question: Why does the Integer class cache values within the range of -128 to 127?

Answer:

The necessity for caching integers in this specific range is rooted in the Java Language Specification. According to the specification, any int or short value between -128 and 127 (inclusive) must be boxed into indistinguishable objects.

The rationale behind this requirement is to ensure consistent behavior for common values while minimizing performance overhead. Caching these values allows for efficient access and comparison, particularly on devices with limited memory resources.

Expansion:

While the lower and upper bounds of the cache range are mandated, the Java implementation is not confined to caching only within this range. The documentation indicates that other values outside of this range may be cached.

To control the maximum size of this cache, Java provides the -XX:AutoBoxCacheMax JVM option. By adjusting this setting, developers can optimize the caching behavior based on their application's specific needs and constraints.

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