Core Java: String concatenation with + evaluates left to right

+ is left-associative, so numeric operands keep adding numerically until a String appears, after which everything to the right concatenates as text; the same numbers print differently depending on where the string sits.

Code

System.out.println(1 + 2 + "=" + 1 + 2);
System.out.println("=" + 1 + 2);

Output

3=12
=12