- Blank lines, spaces, and tabs are white-space characters
- Ignored by compiler
- You can use any number of spaces and line breaks to separate words.
But, you should make program more readable.
- Start with /*, and end by */.
- It can be two or more lines.
- It provides program reader with
information.
- It shows who wrote the program.
- It also shows the purpose of the program.
- The compiler will not read the block.
- Start with //, end at the end of line.
- Tell the compiler to ignore the rest of that particular line.
- It is a place, the programmer can write a remark to remind himself or reader.
Classes are the fundamental building blocks of Java programs.
The keyword public denotes that the class is usable by the "public".
Every Java program consists of at least one class that the programmer define.
That is, there is at least one programmer-defined class.
The file name should be same as the name of the class that includes the main method.
public static void main ( String[] args )
The keyword static indicates that the main method does not operate on an object.
OS starts the program from main method.
Parameter String[] args is required. It is for the runtime system passing information to your application.
For example: Modify your HelloPrinter.java as following:
public class HelloPrinter
{
public static void main(String[] args)
{
System.out.println("Hello, World!");
System.out.println(args[0] + ", nice to meet you!");
}
}
You can compile and run program as following: When you run, you add your input there.
uses the
System class from the core library
to print the "Hello World!" message to standard
output.It is similar to cout<<"Hello World!"<<endl; in C++. In C++, you have to use the header file <iostream>.
