Java is case sensitive language.
Class Names : 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 MyFirstJavaClass
Method Names : All 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()
Program File Name : Name of the program file should exactly match the public class name. there will be only one public class in the program file.if public file name is Sample then file name should be Sample.java
public static void main(String args) - Java program processing starts from the main() method.