javaistic
diff --git a/‎src/pages/docs/constructors.mdx
Lines changed: 330 additions & 0 deletions b/‎src/pages/docs/constructors.mdx
Lines changed: 330 additions & 0 deletions
@@ -0,0 +1,330 @@
+---
+title: Java Constructors
+description: In this tutorial, we will learn how to use the Java constructors with examples.
+---
+
+A constructor in Java is similar to a method that is invoked when an object of the class is created.
+
+Unlike Java methods, a constructor has the same name as that of the class and does not have any return type. For example,
+
+```java
+class Test {
+  Test() {
+    // constructor body
+  }
+}
+```
+Here, `Test()` is a constructor. It has the same name as that of the class and doesn't have a return type.
+
+## Example: Java Constructor
+```java
+class Main {
+  private String name;
+
+  // constructor
+  Main() {
+    System.out.println("Constructor Called:");
+    name = "Javaistic";
+  }
+
+  public static void main(String[] args) {
+
+    // constructor is invoked while
+    // creating an object of the Main class
+    Main obj = new Main();
+    System.out.println("The name is " + obj.name);
+  }
+}
+```
+### Output:
+
+```plaintext
+Constructor Called:
+The name is Javaistic
+```
+In the above example, we have created a constructor named `Main()`.
+
+Inside the constructor, we are initializing the value of the `name` [variable](/docs/variables-literals).
+
+Notice the statement creating an object of the `Main` class.
+
+```java
+Main obj = new Main();
+```
+Here, when the object is created, the `Main()` constructor is called. And the value of the name variable is initialized.
+
+Hence, the program prints the value of the name variables as Javaistic.
+
+## Types of Constructor
+In Java, constructors can be divided into three types:
+
+- [No-Arg Constructor](#1-java-no-arg-constructors)
+- [Parameterized Constructor](#2-java-parameterized-constructor)
+- [Default Constructor](#3-java-default-constructor)
+
+## 1. Java No-Arg Constructors
+
+Similar to methods, a Java constructor may or may not have any parameters (arguments).
+
+If a constructor does not accept any parameters, it is known as a no-argument constructor. For example,
+
+```java
+private Constructor() {
+   // body of the constructor
+}
+```
+### Example: Java Private No-arg Constructor
+```java
+class Main {
+
+  int i;
+
+  // constructor with no parameter
+  private Main() {
+    i = 5;
+    System.out.println("Constructor is called");
+  }
+
+  public static void main(String[] args) {
+
+    // calling the constructor without any parameter
+    Main obj = new Main();
+    System.out.println("Value of i: " + obj.i);
+  }
+}
+```
+#### Output:
+
+```plaintext
+Constructor is called
+Value of i: 5
+```
+In the above example, we have created a constructor Main().
+Here, the constructor does not accept any parameters. Hence, it is known as a no-arg constructor.
+Notice that we have declared the constructor as private.
+Once a constructor is declared private, it cannot be accessed from outside the class.
+
+So, creating objects from outside the class is prohibited using the private constructor.
+Here, we are creating the object inside the same class.
+
+Hence, the program is able to access the constructor. To learn more, visit Java Implement Private Constructor.
+However, if we want to create objects outside the class, then we need to declare the constructor as public.
+
+### Example: Java Public no-arg Constructors
+```java
+class Company {
+  String name;
+
+  // public constructor
+  public Company() {
+    name = "Javaistic";
+  }
+}
+class Main {
+  public static void main(String[] args) {
+
+    // object is created in another class
+    Company obj = new Company();
+    System.out.println("Company name = " + obj.name);
+  }
+}
+```
+#### Output
+
+```plaintext
+Company name = Javaistic
+```
+## 2. Java Parameterized Constructor
+
+A Java constructor can also accept one or more parameters. Such constructors are known as parameterized constructors (constructors with parameters).
+
+### Example: Parameterized Constructor
+```java
+class Main {
+
+  String languages;
+
+  // constructor accepting single value
+  Main(String lang) {
+    languages = lang;
+    System.out.println(languages + " Programming Language");
+  }
+
+  public static void main(String[] args) {
+
+    // call constructor by passing a single value
+    Main obj1 = new Main("Java");
+    Main obj2 = new Main("Python");
+    Main obj3 = new Main("C");
+  }
+}
+```
+#### Output
+
+```plaintext
+Java Programming Language
+Python Programming Language
+C Programming Language
+```
+In the above example, we have created a constructor named `Main()`.
+Here, the constructor takes a single parameter. Notice the expression:
+
+```java
+Main obj1 = new Main("Java");
+```
+Here, we are passing the single value to the constructor.
+Based on the argument passed, the language variable is initialized inside the constructor.
+
+## 3. Java Default Constructor
+
+If we do not create any constructor, the Java compiler automatically creates a no-arg constructor during the execution of the program.
+This constructor is called the default constructor.
+
+### Example: Default Constructor
+```java 
+class Main {
+
+  int a;
+  boolean b;
+
+  public static void main(String[] args) {
+
+    // calls default constructor
+    Main obj = new Main();
+
+    System.out.println("Default Value:");
+    System.out.println("a = " + obj.a);
+    System.out.println("b = " + obj.b);
+  }
+}
+```
+#### Output
+
+```plaintext
+Default Value:
+a = 0
+b = false
+```
+Here, we haven't created any constructors.
+
+Hence, the Java compiler automatically creates the default constructor.
+
+The default constructor initializes any uninitialized instance variables with default values.
+
+| Type	| Default | Value |
+|:-----:|:-------:|:-----:|
+| boolean |	| false |
+| byte |	|	0 |
+| short |	|	0 |
+| int |	|	0 |
+| long |	|	0L |
+| char |	|	\u0000 |
+| float |	|	0.0f |
+| double |	|	0.0d |
+| object|	Reference | null |
+
+To learn more, visit [Java Data Types](/docs/variables-primitive-data-types).
+In the above program, the variables a and b are initialized with default value `0` and `false` respectively.
+
+The above program is equivalent to:
+
+```java
+class Main {
+
+  int a;
+  boolean b;
+
+   Main() {
+    a = 0;
+    b = false;
+  }
+
+  public static void main(String[] args) {
+    // call the constructor
+    Main obj = new Main();
+
+    System.out.println("Default Value:");
+    System.out.println("a = " + obj.a);
+    System.out.println("b = " + obj.b);
+  }
+}
+```
+#### Output
+
+```plaintext
+Default Value:
+a = 0
+b = false
+```
+### Important Notes on Java Constructors
+
+Constructors are invoked implicitly when you instantiate objects.
+
+The two rules for creating a constructor are:
+
+1. The name of the constructor should be the same as the class.
+2. A Java constructor must not have a return type.
+
+If a class doesn't have a constructor, the Java compiler automatically creates a default constructor during run-time. The default constructor initializes instance variables with default values. For example, the int variable will be initialized to 0
+
+### Constructor types:
+No-Arg Constructor - a constructor that does not accept any arguments
+Parameterized constructor - a constructor that accepts arguments
+Default Constructor - a constructor that is automatically created by the Java compiler if it is not explicitly defined.
+A constructor cannot be abstract or static or final.
+A constructor can be overloaded but can not be overridden.
+
+## Constructors Overloading in Java
+Similar to Java method overloading, we can also create two or more constructors with different parameters. This is called constructor overloading.
+
+### Example: Java Constructor Overloading
+```java
+class Main {
+
+  String language;
+
+  // constructor with no parameter
+  Main() {
+    this.language = "Java";
+  }
+
+  // constructor with a single parameter
+  Main(String language) {
+    this.language = language;
+  }
+
+  public void getName() {
+    System.out.println("Programming Language: " + this.language);
+  }
+
+  public static void main(String[] args) {
+
+    // call constructor with no parameter
+    Main obj1 = new Main();
+
+    // call constructor with a single parameter
+    Main obj2 = new Main("Python");
+
+    obj1.getName();
+    obj2.getName();
+  }
+}
+```
+#### Output
+
+```plaintext
+Programming Language: Java
+Programming Language: Python
+```
+In the above example, we have two constructors: `Main()` and `Main(String language)`.
+
+Here, both the constructors initialize the value of the variable language with different values.
+Based on the parameter passed during object creation, different constructors are called, and different values are assigned.
+It is also possible to call one constructor from another constructor. To learn more, visit Java Call One Constructor from Another.
+
+<TipInfo>
+
+**Note:** We have used this keyword to specify the variable of the class. To know more about this keyword, visit [Java this keyword](/docs/this-keyword).
+
+</TipInfo>