Order of addition in Java

Question

In what order does Java add up the numbers a + b + c?
Is it a + (b + c) or (a + b) + c?

I just learned how floating point representation works and finished an exercise which explained that if a, b, c are floats, they might yield a different result when added up in the different ways I wrote above.
That left me wondering which way Java actually does it?

Answer 1

The addition operator is left associative, meaning that a + b + c is evaluated the same as (a + b) + c.

The JLS, Section 15.18, states:

The additive operators have the same precedence and are syntactically left-associative (they group left-to-right).

Answer 2

Left to right (jls-15.18) unless you add parenthesis to alter the order of evaluation.

static int a() {
    System.out.println("a");
    return 1;
}

static int b() {
    System.out.println("b");
    return 1;
}

public static void main(String[] args) {
    System.out.println(a() + b());
}

Output is

a
b
2