What does "+" mean in Java?

This is my answer to this question on Quora.

When dealing with numbers, it adds them like you’d expect.

When dealing with string, it concatenates them. That is, puts one after another into another string.

For example:

1
2
3
4
5
6
7
int x = 5 + 5;
String s = "Me" + "you";
String s2 = "Me" + x + "you";
 
System.out.println(x);
System.out.println(s);
System.out.println(s2);

This outputs the following:

10
Meyou
Me10you

Now try to figure what this outputs:

1
2
String s3 = "Me" + x + 5 + "you";
System.out.println(s3);