About Java programs, it is very important to keep in mind the following points.
Java is case sensitive, which means identifier WORLD and world would have different meaning in Java.
A method names should start with a Lower Case letter. If several words are used to form the name of the method, then each inner word's first letter should be in Upper Case.
Example: public void myMethodName()
For all class names the first letter should be in Upper Case. If several words are used to form a name of the class, each inner word's first letter should be in Upper Case.
Example: class MyFirstClass
Name of the program file should exactly match the class name.When saving the file, you should save it using the class name (Remember Java is case sensitive) and append '.java' to the end of the name (if the file name and the class name do not match, your program will not compile).
Example: Assume 'MyFirstJavaProgram' is the class name. Then the file should be saved as 'MyFirstJavaProgram.java'
public static void main(String args) − Java program processing starts from the main() method which is a mandatory part of every Java program.
All Java components require names. Names used for classes, variables, and methods are called identifiers.
Rules for Identifiers:
- All identifiers should begin with a letter (A to Z or a to z), currency character ($) or an underscore (_).
- After the first character, identifiers can have any combination of characters.
- A key word cannot be used as an identifier.
- Most importantly, identifiers are case sensitive.
- Examples of legal identifiers: age, $salary, _value, __1_value.
- Examples of illegal identifiers: 123abc, -salary.