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Editorial Team
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Asked: 2026-06-14T10:05:50+00:00

Codes : Integer a1 = 100; Integer a2 = 100; System.out.println(a1 == a2); //

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Codes : 

Integer a1 = 100;
Integer a2 = 100;
System.out.println(a1 == a2);   // true

Integer b1 = new Integer(100);
Integer b2 = new Integer(100);
System.out.println(b1 == b2);   // false

Integer c1 = 150;
Integer c2 = 150;
System.out.println(c1 == c2);   // false

Java designs that when using AutoBoxing, values between -128 and 127 appear to refer to the same Integer objects, which causes different results of the first code fragments and the last one

My question is : Why does java design it like this, are there any advantages ?

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1 Answer

  1. Editorial Team

    The simple rationale is that it’s useful/efficient to have a set of Integers already created and available for boxing. It’s very likely that if an application will need boxed integers, they’re going to be in a certain range (e.g. 1… whatever). The fact that they’re boxed up to -127/128 is a simple design heuristic based upon what’s likely to provide benefit without pre-boxing a huge number of integers.

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