JAVA TUTORIALS FOR BEGINNER: core java

Java static method

blogger 0 core java, method, program, programming, static 07:33

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Java
 static method program: static methods in Java can be called without 
creating an object of class. Have you noticed why we write static 
keyword when defining main it's because program execution begins from 
main and no object has been created yet. Consider the example below to 
improve your understanding of static methods.

<h2>
Java static method example program</h2>
<div class="geshifilter">
<pre class="java geshifilter-java" style="font-family: monospace;">class Languages {
 public static void main(String[] args) {
 display();
 }
 
 static void display() {
 System.out.println("Java is my favorite programming language.");
 }
}</pre>
<pre class="java geshifilter-java" style="font-family: monospace;"> </pre>
</div>
Output 
 
<img alt="Java static method program" src="http://www.programmingsimplified.com/images/java/java-static-method-program.png" /> 
 
<h2>
Java static method vs instance method</h2>
Instance method requires an object of its class to be created before 
it can be called while static method doesn't require object creation.

<div class="geshifilter">
<pre class="java geshifilter-java" style="font-family: monospace;">class Difference {
 
 public static void main(String[] args) {
 display(); //calling without object
 Difference t = new Difference();
 t.show(); //calling using object
 }
 
 static void display() {
 System.out.println("Programming is amazing.");
 }
 
 void show(){
 System.out.println("Java is awesome.");
 }
}</pre>
</div>
Output 
 
<img alt="Static vs instance method program" src="http://www.programmingsimplified.com/images/java/static-method-vs-non-static-method.png" /> 
 
<h3>
Using static method of another classes</h3>
If you wish to call static method of another class then you have to 
write class name while calling static method as shown in example below.

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<pre class="java geshifilter-java" style="font-family: monospace;">import java.lang.Math;
 
class Another {
 public static void main(String[] args) {
 int result;
 
 result = Math.min(10, 20); //calling static method min by writing class name
 
 System.out.println(result);
 System.out.println(Math.max(100, 200));
 }
}</pre>
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Output

<div class="geshifilter">
<pre class="java geshifilter-java" style="font-family: monospace;">10
200</pre>
</div>
Here we are using min and max methods of Math class, min returns 
minimum of two integers and max returns maximum of two integers. 
Following will produce an error:

<div class="geshifilter">
<pre class="java geshifilter-java" style="font-family: monospace;">min();</pre>
</div>
We need to write class name because many classes may have a method with same name which we are calling.

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Java static method

Java static method program: static methods in Java can be called without creating an object of class....

Java static block program

blogger 0 core java, program, static, static block 07:31

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Java
 programming language offers a block known as static which is executed 
before main method executes. Below is the simplest example to understand
 functioning of static block later we see a practical use of static 
block.

<h2>
Java static block program</h2>
<div class="geshifilter">
<pre class="java geshifilter-java" style="font-family: monospace;">class StaticBlock {
 public static void main(String[] args) {
 System.out.println("Main method is executed.");
 }
 
 static {
 System.out.println("Static block is executed before main method.");
 }
}</pre>
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Output  
 
 
<img alt="Java static block program" src="http://www.programmingsimplified.com/images/java/java-static-block-program.png" />

Static block can be used to check conditions before execution of main
 begin, Suppose we have developed an application which runs only on 
Windows operating system then we need to check what operating system is 
installed on user machine. In our java code we check what operating 
system user is using if user is using operating system other than 
"Windows" then the program terminates.

<div class="geshifilter">
<pre class="java geshifilter-java" style="font-family: monospace;"> </pre>
<pre class="java geshifilter-java" style="font-family: monospace;"> </pre>
<pre class="java geshifilter-java" style="font-family: monospace;">class StaticBlock {
 public static void main(String[] args) {
 System.out.println("You are using Windows_NT operating system.");
 }
 
 static {
 String os = System.getenv("OS");
 if (os.equals("Windows_NT") != true) {
 System.exit(1);
 }
 }
}</pre>
</div>
 
We are using getenv method of System class which returns value of 
environment variable name of which is passed an as argument to it. 
Windows_NT is a family of operating systems which includes Windows XP, 
Vista, 7, 8 and others.

Output 
 
<img alt="Java static block program" src="http://www.programmingsimplified.com/images/java/java-static-block-program-2.png" />

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Java static block program

Java programming language offers a block known as static which is executed before main method execute...

Java methods

blogger 0 concept, core java, java, methods, program 07:30

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Java
 methods tutorial: Java program consists of one or more classes and a 
class may contain method(s). 
 A class can do very little without methods.
 In this tutorial we will learn about Java methods. Methods are known as
 functions in C and C++ programming languages. A method has a name and 
return type. Main method is a must in a Java program as execution begins
 from it.

<h2>
Syntax of methods</h2>
"Access specifier" "Keyword(s)" "return type" methodName(List of arguments) { 
 // Body of method 
}

Access specifier can be public or private which decides whether other classes can call a method. 
Kewords are used for some special methods such as static or synchronized. 
Return type indicate return value which method returns. 
Method name is a valid Java identifier name.

Access specifier, Keyword and arguments are optional.

Examples of methods declaration: 
public static void main(String[] args); 
void myMethod(); 
private int maximum(); 
public synchronized int search(java.lang.Object);

<h2>
Java Method example program</h2>
<div class="geshifilter">
<pre class="java geshifilter-java" style="font-family: monospace;">class Methods {
 
 // Constructor method
 
 Methods() {
 System.out.println("Constructor method is called when an object of it's class is created");
 }
 
 // Main method where program execution begins
 
 public static void main(String[] args) {
 staticMethod();
 Methods object = new Methods();
 object.nonStaticMethod();
 }
 
 // Static method
 
 static void staticMethod() {
 System.out.println("Static method can be called without creating object");
 }
 
 // Non static method
 
 void nonStaticMethod() {
 System.out.println("Non static method must be called by creating an object");
 }
}</pre>
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Output 
 
 
<img alt="Java methods program output" src="http://www.programmingsimplified.com/images/java/methods-java.png" />

<h2>
Java methods list</h2>
Java has a built in library of many useful classes and there are 
thousands of methods which can be used in your programs. Just call a 
method and get your work done :) . You can find list of methods in a 
class by typing following command on command prompt:

javap package.classname

For example 
javap java.lang.String // list all methods and constants of String class. 
javap java.math.BigInteger // list constants and methods of BigInteger class in java.math package

<h2>
Java String methods</h2>
String class contains methods which are useful for performing 
operations on String(s). Below program illustrate how to use inbuilt 
methods of String class.

<h3>
Java string class program</h3>
<div class="geshifilter">
<pre class="java geshifilter-java" style="font-family: monospace;">class StringMethods
{
 public static void main(String args[])
 {
 int n;
 String s = "Java programming", t = "", u = "";
 
 System.out.println(s);
 
 // Find length of string
 
 n = s.length();
 System.out.println("Number of characters = " + n);
 
 // Replace characters in string
 
 t = s.replace("Java", "C++");
 System.out.println(s);
 System.out.println(t);
 
 // Concatenating string with another string
 
 u = s.concat(" is fun");
 System.out.println(s);
 System.out.println(u);
 }
}</pre>
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Output 
 
<img alt="Java string methods program" src="http://www.programmingsimplified.com/images/java/string-methods-java.png" />

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Java methods

Java methods tutorial: Java program consists of one or more classes and a class may contain meth...

How to get input from user in java

blogger 0 core java, input, program, scanner class, source code, user 07:27

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This
 program tells you how to get input from user in a java program. We are 
using Scanner class to get input from user. This program firstly asks 
the user to enter a string and then the string is printed, then an 
integer and entered integer is also printed and finally a float and it 
is also printed on the screen. Scanner class is present in java.util 
package so we import this package in our program. We first create an 
object of Scanner class and then we use the methods of Scanner class. 
Consider the statement 
 
 Scanner a = new Scanner(System.in);  
 
Here Scanner is the class name, a is the name of object, new 
keyword is used to allocate the memory and System.in is the input 
stream. Following methods of Scanner class are used in the program below
 :- 
1) nextInt to input an integer 
2) nextFloat to input a float 
3) nextLine to input a string

<h2>
 </h2>
<h2>
Java programming source code</h2>
<div class="geshifilter">
<pre class="java geshifilter-java" style="font-family: monospace;">import java.util.Scanner;
 
class GetInputFromUser
{
 public static void main(String args[])
 {
 int a;
 float b;
 String s;
 
 Scanner in = new Scanner(System.in);
 
 System.out.println("Enter a string");
 s = in.nextLine();
 System.out.println("You entered string "+s);
 
 System.out.println("Enter an integer");
 a = in.nextInt();
 System.out.println("You entered integer "+a);
 
 System.out.println("Enter a float");
 b = in.nextFloat();
 System.out.println("You entered float "+b); 
 }
}</pre>
</div>

Output 
 
 
<img alt="user input" src="http://www.programmingsimplified.com/images/java/user-input-java.png" />

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How to get input from user in java

This program tells you how to get input from user in a java program. We are using Scanner class ...

Java program to get ip address

blogger 0 core java, core java interview question, How to, ip address, java, java networking tutorial, program 07:32

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This
 program prints IP or internet protocol address of your computer system.
 InetAddress class of java.net package is used, getLocalHost method 
returns InetAddress object which represents local host. 
<h2>
Java programming source code</h2>
<div class="geshifilter">
<pre class="java geshifilter-java" style="font-family: monospace;">import java.net.InetAddress;
 
class IPAddress
{
 public static void main(String args[]) throws Exception
 {
 System.out.println(InetAddress.getLocalHost());
 }
}</pre>
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Output 
 
 
 
<img alt="IP address" src="http://www.programmingsimplified.com/images/java/ip-address-java.png" /> 
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<a href="http://creativecommons.org/licenses/by-nc-nd/3.0/" rel="license"></a></div>

Java program to get ip address

This program prints IP or internet protocol address of your computer system. InetAddress class of java.net package is used, getLo...

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Java static method

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How to get input from user in java

Java program to get ip address