Java String Concatenation with + operator
java, string
Solution
`+` can represent addition or concatenation.
- If both operands are numeric it is addition.
- If at least one operand is String it is concatenation.
Also addition and concatenation is left associative, so `a+b+c` is same as `(a+b)+c` (the `b` is associated with left `+`).
Taking the first case
20+30+"abc"+(10+10) <--- here both operands are integers with the + operator, which is addition
----- -------
50 +"abc"+ 20 <--- + operator on integer and string results in concatenation
---------
"50abc" + 20 <--- + operator on integer and string results in concatenation
------------
"50abc20"
In the second case:
20+30+"abc"+10+10 <--- here both operands are integers with the + operator, which is addition
-----
50 +"abc"+10+10 <--- + operator on integer and string results in concatenation
---------
"50abc" +10+10 <--- + operator on integer and string results in concatenation
----------
"50abc10" +10 <--- + operator on integer and string results in concatenation
------------
"50abc1010"
Problem
I got confused with the String concatenation. ``` String s1 = 20 + 30 + "abc" + (10 + 10); String s2 = 20 + 30 + "abc" + 10 + 10; System.out.println(s1); System.out.println(s2); ``` The output is: 50abc20 50abc1010 I wonder why 20 + 30 are added together in both cases, but 10 + 10 require parenthese in order to be added (s1) instead of concatenated to the String (s2). Please explain how the String operator `+` works here.