It is very important to keep in mind the basic syntax of java program.
Basic Syntax:
Case Sensitivity - Java is case sensitive, which means identifier Test and test would have different meaning in Java.
Class Names - Class names should be start with upper case letter.If several words are used to form a name of the class, each inner word's first letter should be in Upper Case.
E.g. class MyFirstJavaProgram
Method Names - All method names should be 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.
E.g public void myFirstMethod()
Source File Name - Name of the program file should exactly match the class name.
When saving the file, you should save it using the class name 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.
E.g. : Assume 'Test' is the class name. Then the file should be saved as 'Test.java'
public static void main(String args[]) - Java program execution starts from the main() method which is a mandatory part of every Java program.The main() method should have public and static access modifier,void return type and string array as argument.
If we supply return type other than void then program compile successfully but it's not execute.
Java Identifiers:
All Java components require names. Names used for classes, variables and methods are called identifiers.
In Java, there are several points to remember about identifiers. They are as follows:
1. All identifiers should contains only character(A to Z or a to z),digit (0 to 9) and ( $ , _ ).
2. All identifiers should begin with a letter (A to Z or a to z), dollor character ($) or an underscore ( _ ).
3. After the first character identifiers can have any combination of characters,digits and ($) ,( _ ).
4. A key word cannot be used as an identifier.
5. Identifiers are case sensitive.
Example of identifiers
Legal identifiers: age, $salary, _value , __1_value , abc123,abc_ xyz
Illegal identifiers: 123abc, -salary,@abc,abc!,abc@xyz
Java Modifiers:
There are two types of modifiers in java:
1. Access Modifiers: default, public , protected, private
2. Non-access Modifiers: final, abstract, strictfp,transient,native .
We will see into more details about modifiers in other post.
Java Variables:
We would see following type of variables in Java:
1.Local Variables
2.Class Variables (Static Variables)
3.Instance Variables (Non-static variables)
Basic Syntax:
Case Sensitivity - Java is case sensitive, which means identifier Test and test would have different meaning in Java.
Class Names - Class names should be start with upper case letter.If several words are used to form a name of the class, each inner word's first letter should be in Upper Case.
E.g. class MyFirstJavaProgram
Method Names - All method names should be 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.
E.g public void myFirstMethod()
Source File Name - Name of the program file should exactly match the class name.
When saving the file, you should save it using the class name 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.
E.g. : Assume 'Test' is the class name. Then the file should be saved as 'Test.java'
public static void main(String args[]) - Java program execution starts from the main() method which is a mandatory part of every Java program.The main() method should have public and static access modifier,void return type and string array as argument.
If we supply return type other than void then program compile successfully but it's not execute.
Java Identifiers:
All Java components require names. Names used for classes, variables and methods are called identifiers.
In Java, there are several points to remember about identifiers. They are as follows:
1. All identifiers should contains only character(A to Z or a to z),digit (0 to 9) and ( $ , _ ).
2. All identifiers should begin with a letter (A to Z or a to z), dollor character ($) or an underscore ( _ ).
3. After the first character identifiers can have any combination of characters,digits and ($) ,( _ ).
4. A key word cannot be used as an identifier.
5. Identifiers are case sensitive.
Example of identifiers
Legal identifiers: age, $salary, _value , __1_value , abc123,abc_ xyz
Illegal identifiers: 123abc, -salary,@abc,abc!,abc@xyz
Java Modifiers:
There are two types of modifiers in java:
1. Access Modifiers: default, public , protected, private
2. Non-access Modifiers: final, abstract, strictfp,transient,native .
We will see into more details about modifiers in other post.
Java Variables:
We would see following type of variables in Java:
1.Local Variables
2.Class Variables (Static Variables)
3.Instance Variables (Non-static variables)
Class and Instance variables are global variables.
Java Keywords:
The following list shows the reserved words in Java. These reserved words may not be used as constant or variable or any other identifier names.
| abstract | assert | byte | boolean |
| break | case | catch | char |
| class | const | continue | default |
| do | double | else | enum |
| extends | final | finally | float |
| for | goto | if | implements |
| import | instanceof | int | interface |
| long | native | new | package |
| private | protected | public | return |
| short | static | strictfp | super |
| switch | synchronized | this | throw |
| throws | transient | try | void |
| volatile | while |
Comments in Java:
Java supports single-line and multi-line comments . All statements available inside any comment are ignored by Java compiler.
public class Test{public static void main(String []args){ // This is an example of single line comment /* This is also an example of multi line comment. This is also an example of multi line comment. This is also an example of multi line comment This is also an example of multi line comment */
System.out.println("Hello Collegeone users !"); }
}
