Java identifiers : Using identifiers in java

Identifiers are the names that are provided by programmer. These names can be assigned to any variables, methods, classes, interfaces, etc., java identifiers helps compilers to identify them. Java identifiers can be of any length up to 255 characters. Java identifiers can start with a letter or an undersigned character “_” or a dollar sign “$”. Subsequent characters can be alphabets (both capital and small letters) and numbers from 0 to 9. Space characters or any other special character found on keyboard is not allowed. The only other limitation is that java keywords cannot be used as java identifiers.

Examples of valid identifiers,

1. HelloWorld
2. Hello_World
3. $HelloWorld
4. HelloWorld
5. HELLOWORLD

Examples of invalid identifiers,

1. Hello World
2. HelloWorld #
3. short
4. Hello-World

In the above examples, first have space and space is not allowed in java identifiers. In second “#” and space is present which again not allowed. The third example is invalid as “short” is a java keyword. The last example has “-” symbol and it is also not supported in java identifiers.

The naming conventions above are imposed on the programmer by the compiler. In addition to the above naming conventions, there are certain types of rules that are widely accepted and followed by the programmer community.

It is widely accepted convention to start a class name with capital letter.

Using naming conventions in a java program is a good habit as it makes your program easily readable and understandable to other programmers.