Why Does Java Cache Integers Between -128 and 127?

Why Integer Values Between -128 and 127 Are Cached in Java

In Java, the Integer class employs caching to optimize performance by storing frequently used values between -128 and 127. This caching mechanism ensures consistent object references for common integer values.

Rationale for Caching -128 to 127

The Java Language Specification mandates that an Integer object created from an integer primitive value in this range must always refer to the same object, regardless of the number of conversions. This ensures that these commonly used values are quickly accessible and consistent.

Additional Caching

The Java compiler and virtual machine may cache additional values outside this range based on usage patterns. This is a pragmatic compromise to provide enhanced performance for typical use cases. Smaller devices, for instance, benefit from memory conservation, while larger systems may allow more extensive caching.

Customizing Cache Size

While the range of cached values is generally hard-coded, the Hotspot JVM offers the -XX:AutoBoxCacheMax option to override the default cache size. By specifying this option, developers can adjust the number of cached values according to their requirements, providing more flexibility for specialized scenarios.

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