Java String Concatenation giving output as 2 equals 11 on concat 1+1+"equals"+1+1

Question

I wrote code in java and got output as 2 equals 11.My code is

public class StringPrct 
{
public static void main(String[]args)
{
String s= 1+1+" equals "+1 +1;
System.out.println(s);
}
}

Now the question is why i am not getting output as 2 equals 2.

Answer 1

The + operator has the same precedence whether it's addition or concatenation, and associates left-to-right. So:

1 + 1 + " equals " + 1 + 1

evaluates as

(((1 + 1) + " equals ") + 1) + 1
((2 + " equals ") + 1) + 1
("2 equals " + 1) + 1
"2 equals 1" + 1
"2 equals 11"

If you want to override this, you need to provide parentheses:

1 + 1 + " equals " + (1 + 1)

This becomes:

((1 + 1) + " equals ") + (1 + 1)
(2 + " equals ") + (1 + 1)
"2 equals " + (1 + 1)
"2 equals " + 2
"2 equals 2"

For clarity, you should probably add the parentheses to the first 1 + 1 as well, so that someone reading your code doesn't have to do the mental exercise of adding parentheses and evaluating down:

(1 + 1) + " equals " + (1 + 1)