Why output is 10 for c++ and 9 for java

Question

In c++

int a=4;
int b;
b=a + ++a;
cout<<b; //10

In Java

int a=4;
int b;
b=a + ++a;
System.out.print(b); //9

Answer 1

my guess:
C++
b = a.operator+(++a)
to do the operator function, a must increment, so when the adition is done a is incremented.
java:
execution of an arithmetic expression happens from left to right. so first a is evaluated and then add the incremented one to it, giving 4+5=9, which is assigned to b.

again, its a guess.