Java boxing and unboxing

Question

I have an example in which I cannot determine the number of boxing(s) and unboxing(s), which taking place in the Java code below :

int x = 5;
Integer y = x + x;

From my point of view I see one type of boxing (Integer y = x + x). Am I wrong? Is there any unboxing as well?

You're right. There is no unboxing. – JB Nizet Jan 27 '18 at 11:56 — JB Nizet, Jan 27 '18 at 11:56
@JBNizet Thank you for the response! – ihavename Jan 27 '18 at 12:00 — ihavename, Jan 27 '18 at 12:00

Suresh Atta · Accepted Answer · 2018-01-27T12:27:19.910

2

There is no unboxing. Just boxing happening.

First the expression x+x calculated which is an int and that is boxed to Integer.

So in the whole statement there is no conversion of Integer to int, hence no unboxing.

edited Jan 27 '18 at 12:27

answered Jan 27 '18 at 11:57

Suresh Atta

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Exactly how I thought about it! Thank you for your answer – ihavename Jan 27 '18 at 12:00
`Integer to int` you meant `int to Integer` right ? – Ravi Jan 27 '18 at 12:17
@Ravi I am telling, that is not happening. – Suresh Atta Jan 27 '18 at 12:18
@ꜱᴜʀᴇꜱʜᴀᴛᴛᴀ did you meant *whole statement there is **no** conversion of Integer to int* ? – Ravi Jan 27 '18 at 12:21
Yes. There is only `int` to `Integer`. Not `Integer` to `int`. – Suresh Atta Jan 27 '18 at 12:23
@ꜱᴜʀᴇꜱʜᴀᴛᴛᴀ then you missed ***no*** in your post. :D – Ravi Jan 27 '18 at 12:26
Hello again! I wanted to ask how many boxings and unboxings take place at the code below? `Integer x = 5; int y = x + x;` I would say none, but I am not sure if I am right – ihavename Feb 13 '18 at 10:58

score 1 · Answer 2 · answered Jan 27 '18 at 12:03

As per your question we first define an int value and assign it to x variable (no boxing un-boxing required), Then you are adding 2 integer variable no boxing un-boxing required. Now you are assigning a int result to Integer means changing from primitive to non primitive data type. Java autoboxing can convert int to integer there here autoboxing is there which is boxing.

Java boxing and unboxing

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