When to use post increment and pre increment in Java [duplicate]

Answer 1

In your example it doesn't matter, since you do nothing with the value returned by ++counter.

The only time it makes a difference is when you are using the value returned by the post/pre-increment operator.

For example, if you had a return counter++; or a return ++counter; statement, your method would return a different result based on which operator you used.

Answer 2

PRE-increment is used when you want to use the incremented value of the variable in that expression., whereas POST-increment uses the original value before incrementing it.

Whenever your code encounters a PRE-increment, it increments the value of that variable in the memory, then load that value and continues reading the expression.

POST-increment does the opposite, it loads that value of that variable in the memory, then increments the value and continues reading the expression.

To make it more clear, consider this

int i = counter++;

is equivalent to

int i = counter;
counter = counter + 1;

WHEREAS

int i = ++counter;

is equivalent to

counter = counter + 1;
int i = counter;

EDIT: My StackOverflow comments arent working, so I'll just edit it here.

What I'm saying it, it only matters when you use that value in an expression.

sum = 0
counter = 0;
sum = (++counter)+(++counter)+(counter++)

evaluates as

sum = 0
counter = 0
//For first ++counter
counter = counter + 1
sum = counter

//For second ++counter
counter = counter + 1
sum = sum + counter

//For first counter++
sum = sum + counter
counter = counter + 1