Why are the numbers treated differently

Question

System.out.println(1+2+3+"hello"+4+5);
Outputs:6hello45
The numbers (1,2,3) are treated as integers while (4,5) treated as strings

Answer 1

It's because it reads it from left to right, so in steps:
1+2=3
3+3=6
6+hello=6hello
6hello+4=6hello4 (just adding a number to a string)
6hello4+5=6hello45 (adding a numer to a string again)

If you'd do: 1+2+3+"hello"+(4+5) it would calculate 4+5 instead of adding them to the string

Answer 2

compiler does have some priorities in performing mathematical calculations on different data types. it solves mathematical expression from left to right, on left most it found an int adding into another
1 + 2 = 3 then another int
3+3 = 6 then it found a string and merged it
6 + hello = 6hello now 6hello is a complete string, then it will add 4 in it
6hello + 4 = 6hello4 and then it find int 5 to add in a string
6hello4+5 = 6hello45