why the output of below code is different in c++ and java?

Question

int a =10, b=10;for(int i=0;i<2;i++)
{a = a+ a++; sout("The result of a+ a++ = " +a;)}
for(int i=0;i<2;i++)
{b=b+ ++b;sout("The result of b+ ++b="+b)}

The output of above code in c++ is:-

The result of a+ a++ = 21
The result of a+ a++ = 43
The result of b+ ++b = 22
The result of b+ ++b = 46

but the output of same code in java is:-

The result of a+ a++ = 20
The result of a+ a++ = 40
The result of b+ ++b = 21
The result of b+ ++b = 43
why this strange is happening?

Answer 1

++var increments the value of var before useage.
var++, after useage.
This means that a+ a++
a is initially 10
a is added to a.
a becomes 11.
The sum=20.
b is initially 10
b become 11
b is added to the first b.
The sum=21

Answer 2

How is Java even here?

Answer 3

I m agree with u @$Vengat
but in c++ it gives different output

Answer 4

@Shawn Daley
if c++ evaluate from right to left then comment about this line
a=b-a+(b=a)
this swap a and b

Answer 5

some expressions are well defined, some are not (like k = k++ + ++k). ambiguous expressions valuation depends on the compiler. just avoid them! see:
http://en.cppreference.com/w/cpp/language/eval_order