Simple Java Program
In this section, our plan is to lead you into the
world of Java programming by taking you through the three basic steps required
to get a simple program running. The Java system is a collection of
applications not unlike any of the other applications that you are in touch to
using (such as your word processor, e-mail program, or Internet browser). As
with any application, you need to be sure that Java is properly installed on
your computer. You also need an editor and a terminal application. Here are three
steps to make basic application.
- Create the
program by typing it into a text editor and saving it to a file named,
say, MyProgram.java.
- Compile it
by typing "javac MyProgram.java" in the Command Prompt(cmd).
- Run (or
execute) it by typing "java MyProgram" in the Command
Prompt(cmd).
Creating a Java program. A program is
nothing more than a sequence of characters, like a sentence, a paragraph, or a
poem. To create one, we need to write sequence of characters systematicall just
like we write in e-mail. HelloWorld.java is an example program. Type these
character into your text editor and save it into a file named HelloWorld.java
public
class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello World !!!");
}
}
Note. It is compulsory to give program
name and class name which
contain the public static void main method same.
Compiling a Java program. At first, it might seem to
you as though the Java programming language is designed to be best understood
by the computer. Actually, the language is designed to be best understood by
the programmer (that's you). A compiler is an application that
translates programs from the Java language to a language more suitable for
executing on the computer. It takes a text file with the .java extension as
input (your program) and produces a file with a .class extension (the
computer-language version). To compile go to the path of the file and type
boldfaces text bold boldfaced text below at the cmd.
javac HelloWorld.java
If
you typed in the program correctly, you should see no error messages.
Otherwise, go back and make sure you typed in the program exactly as it appears
above.
Executing a Java program. Once you
compile your program, you can run it. This is the exciting part, where the
computer follows your instructions. To run the HelloWorld program, type the
following at the cmd:
java HelloWorld
Hello World !!!
- Understanding a Java program. The key line with System.out.println() send
the text "Hello World !!!". When we begin to write more
complicated programs, we will discuss the meaning of public, class, main,
String[], args, System.out, and so on.
- Creating your own Java program. For the time being, all of our programs will
be just like HelloWorld.java, except with a different sequence of
statements in main(). The easiest way to write such a program is to:
- Copy HelloWorld.java into a new file whose
name is the program name followed by .java.
- Replace HelloWorld with the program name
everywhere.
- Replace the print statement by a sequence of
statements.
Errors.
Most errors are easily fixed by carefully examining the program as we
create it, in just the same way as we fix spelling and grammatical errors when
we type an e-mail message.
- Compile-time errors. These errors are caught by the system when we
compile the program, because they prevent the compiler from doing the
translation (so it issues an error message that tries to explain why).
- Run-time errors.
These errors are caught by the system when we execute the program, because
the program tries to perform an invalid operation (e.g., division by zero).
- Logical errors.
These errors are (hopefully) caught by the programmer when we execute the
program and it produces the wrong answer. Bugs are the bane of a programmer's
existence. They can be subtle and very hard to find.
One of the very first skills that you will learn is to
identify errors; one of the next will be to be sufficiently careful when coding
to avoid many of them.
Some Idea regarding Java Program:
Hey guys, Here I have provided some more basic examples, kindly follow
it and check output,
Swap Two Number Example using Core Java:
public class SwapElementsExample {
public
static void main(String[] args) {
int num1 = 10;
int num2 = 20;
System.out.println("Before Swapping");
System.out.println("Value of num1 is :"
+ num1);
System.out.println("Value of num2 is :"
+num2);
//swap the value
swap(num1, num2);
}
private
static void swap(int num1, int num2) {
int temp = num1;
num1 = num2;
num2 = temp;
System.out.println("After Swapping");
System.out.println("Value of num1 is :"
+ num1);
System.out.println("Value of num2 is :"
+num2);
}
}
|
Reverse No. Example Using Core Java
public class ReverseNumber {
public static void main(String[] args) {
//original number
int number = 1234;
int reversedNumber = 0;
int temp = 0;
while(number > 0){
//use modulus operator
to strip off the last digit
temp = number%10;
//create the reversed
number
reversedNumber =
reversedNumber * 10 + temp;
number = number/10;
}
//output the reversed number
System.out.println("Reversed Number is: "
+ reversedNumber);
}
}
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