Why does `c == d` return `true` for `Integer c = 100` and `Integer d = 100` in Java?

Integer Caching in Java

Query:

In Java, why does the comparison c == d evaluate to true despite being distinct Integer objects (c = 100 and d = 100)?

Response:

To enhance performance and memory utilization, Java employs a cache for integer objects within the range of -128 to 127. Consequently, c and d refer to the same cached instance.

Purpose of the Optimization:

• Memory Conservation: By caching common integer values, Java saves substantial memory space compared to creating separate objects for each distinct value.
• Cache Efficiency: Caching frequently used integer values improves cache performance by minimizing cache misses.

Benefits:

• Enhanced Performance: Reduced memory consumption and improved cache efficiency lead to faster code execution.
• Optimized Memory Utilization: Caching integers frees up valuable memory resources for other applications.

Research

The following references provide further insights into this topic:

• [Java Platform SE 8 Language Specification](https://docs.oracle.com/javase/specs/jls/se8/html/jls-5.html#jls-5.1.7)
• [Autoboxing Tutorial](https://docs.oracle.com/javase/tutorial/java/data/autoboxing.html)

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