Integer caching

Repharse

• Why 1 == 1 is true but 1000 == 1000 is false when dealing with wrapper classes?

JVM caches object of wrapper classes (Integer, Byte, Short, Character, and Long) with values in the range -128 to 127.

When you assign an Integer with a value within this range, you get the same instance from the cache.

Integer a = 1; // cached instance
Integer b = 1; // cached instance
System.out.println(a == b); // true as both refer to same instance

When the value is outside the caching range, a new object is created for each assignment.

Integer a = 1000; // cached instance
Integer b = 1000; // cached instance
System.out.println(a == b); // false as both refer to different instance