Hello Program Example:
class HelloProgram{
public static void main(String args[]){
System.out.println("Hello Intellipaat");//It will print Hello Intellipaat
}
}
Type this program in notepad and save it as Hello.java.
Type below commands to Compile and execute the above program:
javac HelloProgram.java
java HelloProgram
Output
Hello Intellipaat
Program Explanation
- class: This keyword is used to declare a class in java.
- public: It is an access modifier that represents visibility. It means it is visible to all.
- static: It is a keyword. The advantage of static method is that there is no need to create object to invoke the static method if it is non static method, JVM creates objects then call main () method, this will give the problem of extra memory location. That’s why main() method is become static.
- void: It is the return type that means it doesn’t return any value.
- main: It represents the startup of the program. Without main program cannot run.
- String[] args: It tells that the main() has a parameter which is an array of String references. This array is created by the Java system just before main() acquires control. The elements of the array refer toStrings that hold text from the command line that starts the program.
- System.out.println(): It is used print statement which is inside the ().
Java Comments
It is useful to place a comment in place to indicate what you are doing. It is added into the program for making the program easier to understand and these are not compiled by the compiler or interpreter. It is useful if you want someone else to be able to ever read your code.
There are two ways to declare comment in java which are as follows:
- Single Line comment
- Multi Line comment
- Single Line comment – It is used to apply the comment on a single line. To apply single line comment // is used.
e.g.
System.out.println("Hello Intellipaat"); // It will print Hello Intellipaat
Multi Line comment – It is used to apply the comment on multiple lines. e.g.
System.out.println("Hello Intellipaat"); /* It will print
Hello intellipaat */
Keywords in Java
Keywords are also known as reserved words which express a special meaning to the compiler and interpreter. Keywords in java are –
| abstract | assert | boolean | break |
| byte | 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 | | |