Java Reference
In-Depth Information
Display 1.1
A Sample Java Program
Name of class
(program)
1
public class
FirstProgram
2 {
3
public static void
main(String[] args)
4 {
5 System.out.println("Hello reader.");
6 System.out.println("Welcome to Java.");
The
main
method
7 System.out.println("Let's demonstrate a simple calculation.");
8
int
answer;
9 answer = 2 + 2;
10 System.out.println("2 plus 2 is " + answer);
11 }
12 }
Sample Dialogue
Hello reader.
Welcome to Java.
Let's demonstrate a simple calculation.
2 plus 2 is 4
The next two lines, shown in what follows, are the first actions the program
performs:
println
System.out.println("Hello reader.");
System.out.println("Welcome to Java.");
Each of these lines begins with
System.out.println
. Each one causes the quoted
string given within the parentheses to be output to the screen. For example, consider
System.out.println("Hello reader.");
This causes the line
Hello reader.
to be written to the screen. The output produced by the next line that begins with
System.out.println
will go on the following line. Thus, these two lines cause the
following output:
Hello reader.
Welcome to Java.
These lines that begin with
System.out.println
are a way of saying “output what
is shown in parentheses,” and the details of why the instruction is written this way need
not concern us yet. However, we can tell you a little about what is going on here.
System.out.
println
