Understanding Java Integer Caching and Autoboxing: Interview Questions Explained

The first interview question demonstrates that Integer a = 888; and Integer b = 888; compare false because values outside the cache range (-128 to 127) are boxed into distinct objects, while Integer c = 88; and Integer d = 88; compare true due to caching.

Java's autoboxing translates Integer a = 888; to Integer a = new Integer(888); , creating a new object each time, whereas values within the cache range are obtained via Integer.valueOf(int i) , which returns a shared instance from IntegerCache .

The relevant source code shows public static Integer valueOf(int i) { if (i >= IntegerCache.low && i <= IntegerCache.high) return IntegerCache.cache[i + (-IntegerCache.low)]; return new Integer(i); } and the static initializer that fills the cache array with Integer objects for -128 to 127.

The second question creates Integer a = new Integer(88); , passes it to test(Integer integer) , and reassigns the parameter to new Integer(99); . Because Java passes arguments by value (the reference is copied), the original a remains unchanged, so the program prints 88 .

The third question assigns a = 99; after a = new Integer(88); . The assignment autoboxes the primitive 99 using Integer.valueOf(99) , which returns the cached Integer instance for 99, effectively changing the reference of a to a new object, so the output is 99 .

Overall, the article clarifies how Java's Integer caching, autoboxing, and pass‑by‑value semantics influence object identity and output in typical interview code snippets.