Create First Program
In this section, you will learn to write a simple Java program. For developing a java program you just need a simple text editor like "notepad".
Open the notepad and write your program.
Let's create a class createfirstprogram that will print a message "Welcome to RoseIndia.net" on the console.
Here is the video tutorial of: "Learn Java in a day - Create First Program"
Here is the code of createfirstprogram.java file:
Save this program in the specified directory ("C:\Vinod" in this example) with name createfirstprogram.java.
This class contains public, static and void java keywords (these are pre-defined words in java which carries specific meaning).
public keyword specifies the
accessibility issues of a class. Here, It specifies that method can be accessed from anywhere.
static keyword indicates that this method can be invoked simply by using the name of the class without creating any class-object.
void keyword specifies that this method will not return any type of data.
main() method is the main entry point of the program, to start execution. First of all JVM calls the main method of a class and start execution . JVM (Java Virtual Machine) is responsible for running java programs.
args is a string array that takes values from java command line. It's index starts from '0'. We can access values by writing args, args etc.
println() function prints the output to the standard output stream (monitor).
out represents the standard output stream (monitor).
Now, you are ready to compile and run this program. Open the command prompt and go to the directory ("C:\vinod" in this example) where your program is saved.
Java uses the "javac" command to compile your program (Type javac createfirstprogram.java) . After compiling successfully, you can run it. Java uses the "java" command to execute your program (Type java createfirstprogram). It will print "Welcome to RoseIndia.net".
Output of program:
Welcome to RoseIndia.net