How do the post increment (i++) and pre increment (++i) operators work in Java?

Question

Can you explain to me the output of this Java code?

int a=5,i;

i=++a + ++a + a++;
i=a++ + ++a + ++a;
a=++a + ++a + a++;

System.out.println(a);
System.out.p         


        

Answer 1

Presuming that you meant

int a=5; int i;

i=++a + ++a + a++;

System.out.println(i);

a=5;

i=a++ + ++a + ++a;

System.out.println(i);

a=5;

a=++a + ++a + a++;

System.out.println(a);

This evaluates to:

i = (6, a is now 6) + (7, a is now 7) + (7, a is now 8)

so i is 6 + 7 + 7 = 20 and so 20 is printed.

i = (5, a is now 6) + (7, a is now 7) + (8, a is now 8)

so i is 5 + 7 + 8 = 20 and so 20 is printed again.

a = (6, a is now 6) + (7, a is now 7) + (7, a is now 8)

and after all of the right hand side is evaluated (including setting a to 8) THEN a is set to 6 + 7 + 7 = 20 and so 20 is printed a final time.