Integer cache -128..127 — identity surprises?

Integer caching

Autoboxing converts primitives to wrappers. For Integer, Byte, Short, Character, and Long in a default range, the JVM returns cached instances—so == may be true for small values but false for larger ones.

• Default Integer cache: -128 to 127 (configurable via -XX:AutoBoxCacheMax).
• Always use equals or intValue() comparison for business logic.
• new Integer(5) always new object (deprecated constructors removed in modern JDK).
• Surprises in Map<Integer, ?> keys when mixing literals and parsed ints.

Integer a = 127, b = 127;
Integer c = 128, d = 128;
System.out.println(a == b); // true (cached)
System.out.println(c == d); // false (distinct objects)