JAVA TUTORIALS FOR BEGINNER: code

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Constructor
 java tutorial: Java constructors are the methods which are used to 
initialize objects. Constructor method has the same name as that of 
class, they are called or invoked when an object of class is created and
 can't be called explicitly. Attributes of an object may be available 
when creating objects if no attribute is available then default 
constructor is called, also some of the attributes may be known 
initially. It is optional to write constructor method in a class but due
 to their utility they are used.

<h2>
Java constructor example</h2>
<div class="geshifilter">
<pre class="java geshifilter-java" style="font-family: monospace;">class Programming {
 //constructor method
 Programming() {
 System.out.println("Constructor method called.");
 }
 
 public static void main(String[] args) {
 Programming object = new Programming(); //creating object
 }
}</pre>
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Output 
 
<img alt="Java constructor example" src="http://www.programmingsimplified.com/images/java/constructor-java.png" /> 
This code is the simplest example of constructor, we create class 
Programming and create an object, constructor is called when object is 
created. As you can see in output "Constructor method called." is 
printed.

<h2>
Java constructor overloading</h2>
Like other methods in java constructor can be overloaded i.e. we can 
create as many constructors in our class as desired. Number of 
constructors depends on the information about attributes of an object we
 have while creating objects. See constructor overloading example:

<div class="geshifilter">
<pre class="java geshifilter-java" style="font-family: monospace;"> </pre>
<pre class="java geshifilter-java" style="font-family: monospace;">class Language {
 String name;
 
 Language() {
 System.out.println("Constructor method called.");
 }
 
 Language(String t) {
 name = t;
 }
 
 public static void main(String[] args) {
 Language cpp = new Language();
 Language java = new Language("Java");
 
 cpp.setName("C++");
 
 java.getName();
 cpp.getName();
 }
 
 void setName(String t) {
 name = t;
 }
 
 void getName() {
 System.out.println("Language name: " + name);
 }
}</pre>
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Output 
 
<img alt="Java constructor overloading program" src="http://www.programmingsimplified.com/images/java/constructor-overloading-java.png" />

When cpp object is created default constructor is called and when java object is created constructor with argument is called, setName method is used to set 'name' attribute of language, getName method prints language name.

<h2>
Java constructor chaining</h2>
Constructor chaining occurs when a class inherits another class i.e. 
in inheritance, as in inheritance sub class inherits the properties of 
super class. Both the super and sub class may have constructor methods, 
when an object of sub class is created it's constructor is invoked it 
initializes sub class attributes, now super class constructor needs to 
be invoked, to achieve this java provides a <code class="java geshifilter-java">super</code>
 keyword through which we can pass arguments to super class constructor.
 For more understanding see constructor chaining example:

<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 GrandParent {
 int a;
 
 GrandParent(int a) {
 this.a = a;
 }
}
 
class Parent extends GrandParent {
 int b;
 
 Parent(int a, int b) {
 super(a);
 this.b = b;
 }
 
 void show() {
 System.out.println("GrandParent's a = " + a);
 System.out.println("Parent's b = " + b);
 }
}
 
class Child {
 public static void main(String[] args) {
 Parent object = new Parent(8, 9);
 object.show();
 }
}</pre>
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Output 
 
 
<img alt="Java constructor chaining program example" src="http://www.programmingsimplified.com/images/java/constructor-chaining-java.png" />

Constructor method doesn't specify a return type, they return instance of class itself.

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Java constructor tutorial with code examples

Constructor java tutorial: Java constructors are the methods which are used to initialize objects. Co...

JAVA TUTORIALS FOR BEGINNER

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Java constructor tutorial with code examples