Why can Object[] store primitives?

Question

Object[] can store any object from any class because every class in Java extends java.lang.Object.

I don't think primitives extend from Object, so why can we store them like the following?

Object[] obj_arr = {1, 2, 1.2, 'a', false, new MyClass(), null};

The question is why can primitives be stored in an Object array and did Auto boxing happen or not in the above code?

Pretty sure you could check the auto boxing yourself using `instanceof`, no? — OneCricketeer, Jun 12 '16 at 18:48
When you run the code, autoboxing will change `1` and `2` to their wrapper types. — sguan, Jun 12 '16 at 19:08
Related : http://stackoverflow.com/questions/27647407/why-do-we-use-autoboxing-and-unboxing-in-java — Yassin Hajaj, Jun 12 '16 at 19:15

Óscar López · Accepted Answer · 2016-06-12T18:59:19.323

7

The primitive types get auto-boxed into their respective wrapper types, so for instance: 1 becomes Integer.valueOf(1) and that's an instance of the Integer class which extends from Object, hence it can be stored into an Object[]. The same thing happens for the other primitives - instances of Double, Character and Boolean are used in place of the corresponding primitive values.

edited Jun 12 '16 at 18:59

answered Jun 12 '16 at 18:48

Óscar López

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Actually, autoboxing doesn't replace `1` by `new Integer(1)` but by `Integer.valueOf(1)`, which may return a cached `Integer` object. – Jesper Jun 12 '16 at 18:58

Why can Object[] store primitives?

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