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Learn more about Teams Why doesn't the post increment operator work on a method that returns an int? (11 answers) if (questions.size() >= answers.size()) { answers.forEach(answer -> { if (questions.contains(answer)) this.answer.setPoints((this.answer.getPoints())++); // Variable expected ^

The error I encountered is:

unexpected type
required: variable
found: value

What is wrong with the statement?

this.answer.setPoints((this.answer.getPoints())++);
                If postincrement works the same in Java as it does in C (quite likely) then even if the syntax was correct, you'd still end up with the same value ...
– Jongware
                Mar 22, 2016 at 21:40
The ++ operator only makes sense when applied to a declared variable.
This operator will add one to an integer, long, etc. and save the result to the same variable in-place.
If there is no declared variable, there is nowhere to save the result, which is why the compiler complains.
One way to allow use of the ++ operator in this situation would be (not the most concise code, but to illustrate the point):
int myVariable = this.answer.getPoints();
myVariable++;
this.answer.setPoints(myVariable);
this.answer.getPoints() will return a value, and you can't use increment ++ or decrement -- on that. You can only use it on variables.
If you want to add 1 to it, you can do it as:
this.answer.setPoints((this.answer.getPoints())+1);
++ will increment a variable with 1, but since this.answer.getPoints() will return a value and its not a defined variable, it won't be able to store the incremented value.
Think of it like doing:
this.answer.getPoints() = this.answer.getPoints() + 1, where would the incremented value be stored?
                @AndrewTobilko because you can't modify the return value of a method, and ++ modifies the variable it's used on?
– Louis Wasserman
                Mar 22, 2016 at 21:43
The first part of this (this.answer.getPoints()) creates an rvalue: effectively, an anonymous variable that lasts almost no time.
The second part ++ increments that anonymous variable after it is passed into setPoints().
Then, the anonymous variable (now incremented) is thrown away.
The compiler/IDE knows that you're doing something that will never be used (incrementing a temporary value), and is flagging it.