It is natural to think of a char as a String of length 1. Unfortunately, in Java the char and String types are incompatible since a String is a reference type and a char is a primitive type. Some of the limitations of this incompatibility are:

1. You cannot pass a char argument to a String parameter (nor the opposite).
2. You cannot use a char constant in place of a String constant.
3. You cannot assign a char expression to a String variable (nor the opposite).

The last restriction is particularly troublesome, because there are many times in programs when char data and String data must be used cooperatively.

Extracting a char from within a String can be accomplished using the charAt method as previously described.

Conversion from char to String can be accomplished by using the "+" (concatenation) operator described previously. Concatenating any char with an empty string (String of length zero) results in a string that consists of that char. The java notation for an empty string is two consecutive double quotation marks. For example, the following expression

"" + 'X';

evaluates to a String of length 1, consisting of the letter "X"

// charVar is a variable of type char
// stringVar is a variable of type String
stringVar = "" + charVar;

The execution of this instruction assigns to stringVar a String object that consist of the single character from charVar.