If a = b, what happens if each value changes respectively?

Question

What happens if you change the variable b, or what if you change a. What does the order have to do with anything.

I know count = count + 1 but the two variables is messing up my brain.

b = 7;
a = 7;
a = b;
a += 1;

What happens to b?

Please post a complete, reproducible snippet of code and add the Java tag. You can do so using the "edit" link. — Kyll, Jun 17 '15 at 11:16
Do you know about raw types? Instances, references? Short answer: If b would change, it would mess up not only your head but everyone's. It'd make life a lot harder. — runDOSrun, Jun 17 '15 at 11:25
Ok but why does this have to be down voted. This community is really hostile. I was in an environment where I couldn't run my code (school library) — Tastybot, Jun 17 '15 at 12:25

aioobe · Accepted Answer · 2015-06-17T11:45:19.263

8

What happens to b?

Nothing happens to b.

When you do

a = b;

you're copying the value stored in b and putting it in a. (You're not making a an alias of b.)

When you then do a += 1; you're changing the value stored in a (and the value stored in b remains unchanged).

You can verify this by printing the final values after your code snippet:

System.out.println(a);  // prints 8
System.out.println(b);  // prints 7

What happens if you change the variable b, or what if you change a. What does the order have to do with anything.

a and b are two independent variables and changing one will never affect the other.

The order matters since when you do a = b the value of b is copied into a and whatever a stored before is discarded. If you had done a += 1 prior to a = b, then a would have been restored to 7 again.

edited Jun 17 '15 at 11:45

answered Jun 17 '15 at 11:19

aioobe

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Yeah I did. Also, why does this have downvotes? I wasn't able to print or do anything because I was at the library and couldn't run code. – Tastybot Jun 17 '15 at 12:30
That's not a very common situation to be in so I think people just downvoted for "lack of effort". A future tip, you can use http://ideone.com (example: http://ideone.com/xaoGwm). – aioobe Jun 17 '15 at 12:37

Milkmaid · Answer 2 · 2015-06-17T11:28:22.060

2

int is raw type you don't copy reference but the value itself. This will work same way for Integer because it is immutable class.

 int b = 7;
 int a = 7;
 a = b;
 a+=1;
 System.out.println(a);// ->8
 System.out.println(b);// ->7

edited Jun 17 '15 at 11:28

answered Jun 17 '15 at 11:19

Milkmaid

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Your reference to `Integer` is a bit confusing. There's more to it than just immutability. (You wouldn't be able to do `+=` if it wasn't for autoboxing for instance.) – aioobe Jun 17 '15 at 11:32
@aioobe for sure more info [here](http://stackoverflow.com/a/3085357/4327527) I just want to avoid confusing why some classes does not works as reference. – Milkmaid Jun 17 '15 at 11:36

score 1 · Answer 3 · answered Jun 17 '15 at 11:19

1

Still 7. integer is raw type and if you assign a int variable to another int, just its value is received by the new one. Not the object itself.

answered Jun 17 '15 at 11:19

Asqan

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score 1 · Answer 4 · answered Jun 17 '15 at 11:21

1

b stays 7.
a becomes 8.

You could use System.out.println(); to print values of variables and find out yourself if you ever doubt. That or use the debugger.

answered Jun 17 '15 at 11:21

Vahx

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score 1 · Answer 5 · answered Jun 17 '15 at 11:23

public static void main(String[] args) {
        int b = 7; // b points to 7
        int a = 7; // a points to 7
        a = b; // b and a points to 7
        a += 1; // a points to 8 now, b is still pointing to 7
        System.out.println(a);
        System.out.println(b);
    }

output

8
7

When we do a += 1; we change the value stored in a (value stored in b is still same).

If a = b, what happens if each value changes respectively?

5 Answers5