Final variable printing in java

Question

final int a=5;
System.out.println(a+1)

prints 6 whereas System.out.println(a++) or a=a+1 and then sop(a) would give error.

Why would it print 6 when final values cant be changed?

Answer 1

Both a++ and a=a+1 assign a new value to a .

a+1 does not: it just evaluates to 1 more than the value in a .

Evaluating the statements:

System.out.println(a);
System.out.println(a+1);
System.out.println(a);

will show that the value of a is the same before and after. Doing the same with a++ or a=a+1 in the middle statement (obviously making a non-final first) will show that a is changed.

This should be no more surprising than System.out.println(5+1) printing 6, whilst leaving the values of 5 and 1 unchanged.

Answer 2

Because you never modify a in your example. You print the result of a+1 . If you print a afterwards you'll see that it is still 5 .

It is basically

int a = 5;
int b = a+1;
System.out.println(b); // prints 6
System.out.println(a); // still prints 5