{"id":1202,"date":"2022-02-25T16:45:51","date_gmt":"2022-02-25T16:45:51","guid":{"rendered":"https:\/\/mdr.foobrdigital.com\/?p=1202"},"modified":"2022-02-25T16:45:51","modified_gmt":"2022-02-25T16:45:51","slug":"java-inheritance-2","status":"publish","type":"post","link":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/2022\/02\/25\/java-inheritance-2\/","title":{"rendered":"Java Inheritance"},"content":{"rendered":"\n

In this tutorial, we will learn about Java inheritance and its types with the help of example.<\/p>\n\n\n\n

Inheritance is one of the key features of OOP that allows us to create a new class from an existing class.<\/p>\n\n\n\n

The new class that is created is known as subclass<\/strong> (child or derived class) and the existing class from where the child class is derived is known as superclass<\/strong> (parent or base class).<\/p>\n\n\n\n

The extends<\/code> keyword is used to perform inheritance in Java. For example,<\/p>\n\n\n\n

class Animal {\n  \/\/ methods and fields\n}\n\n\/\/ use of extends keyword\n\/\/ to perform inheritance\nclass Dog extends Animal {\n\n  \/\/ methods and fields of Animal\n  \/\/ methods and fields of Dog\n}<\/code><\/pre>\n\n\n\n
In the above example, the Dog<\/var> class is created by inheriting the methods and fields from the Animal<\/var> class.<\/p>\n\n\n\n
Here, Dog<\/var> is the subclass and Animal<\/var> is the superclass.<\/p>\n\n\n\n
\n\n\n\n
Example 1: Java Inheritance<\/h3>\n\n\n\n
class Animal {\n\n  \/\/ field and method of the parent class\n  String name;\n  public void eat() {\n    System.out.println(\"I can eat\");\n  }\n}\n\n\/\/ inherit from Animal\nclass Dog extends Animal {\n\n  \/\/ new method in subclass\n  public void display() {\n    System.out.println(\"My name is \" + name);\n  }\n}\n\nclass Main {\n  public static void main(String[] args) {\n\n    \/\/ create an object of the subclass\n    Dog labrador = new Dog();\n\n    \/\/ access field of superclass\n    labrador.name = \"Rohu\";\n    labrador.display();\n\n    \/\/ call method of superclass\n    \/\/ using object of subclass\n    labrador.eat();\n\n  }\n}<\/code><\/pre>\n\n\n\n
Output<\/strong><\/p>\n\n\n\n
My name is Rohu\nI can eat<\/samp><\/code><\/pre>\n\n\n\n
In the above example, we have derived a subclass Dog<\/var> from superclass Animal<\/var>. Notice the statements,<\/p>\n\n\n\n
labrador.name = \"Rohu\";\n\nlabrador.eat();<\/code><\/pre>\n\n\n\n
Here, labrador<\/var> is an object of Dog<\/var>. However, name<\/var> and eat()<\/code> are the members of the Animal<\/var> class.<\/p>\n\n\n\n
Since Dog<\/var> inherits the field and method from Animal<\/var>, we are able to access the field and method using the object of the Dog<\/var>.<\/p>\n\n\n\n
\"Subclass
Java Inheritance Implementation<\/figcaption><\/figure>\n\n\n\n
\n\n\n\n
is-a relationship<\/h2>\n\n\n\n
In Java, inheritance is an is-a<\/strong> relationship. That is, we use inheritance only if there exists an is-a relationship between two classes. For example,<\/p>\n\n\n\n
  • Car<\/strong> is a Vehicle<\/strong><\/li>
  • Orange<\/strong> is a Fruit<\/strong><\/li>
  • Surgeon<\/strong> is a Doctor<\/strong><\/li>
  • Dog<\/strong> is an Animal<\/strong><\/li><\/ul>\n\n\n\n
    Here, Car<\/strong> can inherit from Vehicle<\/strong>, Orange<\/strong> can inherit from Fruit<\/strong>, and so on.<\/p>\n\n\n\n
    \n\n\n\n
    Method Overriding in Java Inheritance<\/h2>\n\n\n\n
    In Example 1<\/strong>, we see the object of the subclass can access the method of the superclass.<\/p>\n\n\n\n
    However, if the same method is present in both the superclass and subclass, what will happen?<\/strong><\/p>\n\n\n\n
    In this case, the method in the subclass overrides the method in the superclass. This concept is known as method overriding in Java.<\/p>\n\n\n\n
    Example 2: Method overriding in Java Inheritance<\/h3>\n\n\n\n
    class Animal {\n\n  \/\/ method in the superclass\n  public void eat() {\n    System.out.println(\"I can eat\");\n  }\n}\n\n\/\/ Dog inherits Animal\nclass Dog extends Animal {\n\n  \/\/ overriding the eat() method\n  @Override\n  public void eat() {\n    System.out.println(\"I eat dog food\");\n  }\n\n  \/\/ new method in subclass\n  public void bark() {\n    System.out.println(\"I can bark\");\n  }\n}\n\nclass Main {\n  public static void main(String[] args) {\n\n    \/\/ create an object of the subclass\n    Dog labrador = new Dog();\n\n    \/\/ call the eat() method\n    labrador.eat();\n    labrador.bark();\n  }\n}<\/code><\/pre>\n\n\n\n
    Output<\/strong><\/p>\n\n\n\n
    I eat dog food\nI can bark<\/samp><\/code><\/pre>\n\n\n\n
    In the above example, the eat()<\/code> method is present in both the superclass Animal<\/var> and the subclass Dog<\/var>.<\/p>\n\n\n\n
    Here, we have created an object labrador<\/var> of Dog<\/var>.<\/p>\n\n\n\n
    Now when we call eat()<\/code> using the object labrador<\/var>, the method inside Dog<\/var> is called. This is because the method inside the derived class overrides the method inside the base class.<\/p>\n\n\n\n
    This is called method overriding.<\/p>\n\n\n\n
    Note<\/strong>: We have used the\u00a0@Override<\/code>\u00a0annotation to tell the compiler that we are overriding a method. However, the annotation is not mandatory.<\/p>\n\n\n\n
    \n\n\n\n
    super Keyword in Java Inheritance<\/h2>\n\n\n\n
    Previously we saw that the same method in the subclass overrides the method in superclass.<\/p>\n\n\n\n
    In such a situation, the super<\/code> keyword is used to call the method of the parent class from the method of the child class.<\/p>\n\n\n\n
    Example 3: super Keyword in Inheritance<\/h3>\n\n\n\n
    class Animal {\n\n  \/\/ method in the superclass\n  public void eat() {\n    System.out.println(\"I can eat\");\n  }\n}\n\n\/\/ Dog inherits Animal\nclass Dog extends Animal {\n\n  \/\/ overriding the eat() method\n  @Override\n  public void eat() {\n\n    \/\/ call method of superclass\n    super.eat();\n    System.out.println(\"I eat dog food\");\n  }\n\n  \/\/ new method in subclass\n  public void bark() {\n    System.out.println(\"I can bark\");\n  }\n}\n\nclass Main {\n  public static void main(String[] args) {\n\n    \/\/ create an object of the subclass\n    Dog labrador = new Dog();\n\n    \/\/ call the eat() method\n    labrador.eat();\n    labrador.bark();\n  }\n}<\/code><\/pre>\n\n\n\n
    Output<\/strong><\/p>\n\n\n\n
    I can eat\nI eat dog food\nI can bark <\/samp><\/code><\/pre>\n\n\n\n
    In the above example, the eat()<\/code> method is present in both the base class Animal<\/var> and the derived class Dog<\/var>. Notice the statement,<\/p>\n\n\n\n
    super.eat();<\/code><\/pre>\n\n\n\n
    Here, the super<\/code> keyword is used to call the eat()<\/code> method present in the superclass.<\/p>\n\n\n\n
    We can also use the\u00a0super<\/code>\u00a0keyword to call the constructor of the superclass from the constructor of the subclass. <\/p>\n\n\n\n
    \n\n\n\n
    protected Members in Inheritance<\/h2>\n\n\n\n
    In Java, if a class includes protected<\/code> fields and methods, then these fields and methods are accessible from the subclass of the class.<\/p>\n\n\n\n
    Example 4: protected Members in Inheritance<\/h3>\n\n\n\n
    class Animal {\n  protected String name;\n\n  protected void display() {\n    System.out.println(\"I am an animal.\");\n  }\n}\n\nclass Dog extends Animal {\n\n  public void getInfo() {\n    System.out.println(\"My name is \" + name);\n  }\n}\n\nclass Main {\n  public static void main(String[] args) {\n\n    \/\/ create an object of the subclass\n    Dog labrador = new Dog();\n\n    \/\/ access protected field and method\n    \/\/ using the object of subclass\n    labrador.name = \"Rocky\";\n    labrador.display();\n\n    labrador.getInfo();\n  }\n}<\/code><\/pre>\n\n\n\n
    Output<\/strong><\/p>\n\n\n\n
    I am an animal.\nMy name is Rocky<\/samp><\/code><\/pre>\n\n\n\n
    In the above example, we have created a class named Animal. The class includes a protected field: name<\/var> and a method: display()<\/code>.<\/p>\n\n\n\n
    We have inherited the Dog<\/var> class inherits Animal<\/var>. Notice the statement,<\/p>\n\n\n\n
    labrador.name = \"Rocky\";\nlabrador.display();<\/code><\/pre>\n\n\n\n
    Here, we are able to access the protected field and method of the superclass using the labrador<\/var> object of the subclass.<\/p>\n\n\n\n
    \n\n\n\n
    Why use inheritance?<\/h2>\n\n\n\n
    • The most important use of inheritance in Java is code reusability. The code that is present in the parent class can be directly used by the child class.<\/li>
    • Method overriding is also known as runtime polymorphism. Hence, we can achieve Polymorphism in Java with the help of inheritance.<\/li><\/ul>\n\n\n\n
      \n\n\n\n
      Types of inheritance<\/h2>\n\n\n\n
      There are five types of inheritance.<\/p>\n\n\n\n
      1. Single Inheritance<\/h3>\n\n\n\n
      In single inheritance, a single subclass extends from a single superclass. For example,<\/p>\n\n\n\n
      \"Class
      Java Single Inheritance<\/figcaption><\/figure>\n\n\n\n
      \n\n\n\n
      2. Multilevel Inheritance<\/h3>\n\n\n\n
      In multilevel inheritance, a subclass extends from a superclass and then the same subclass acts as a superclass for another class. For example,<\/p>\n\n\n\n
      \"Class
      Java Multilevel Inheritance<\/figcaption><\/figure>\n\n\n\n
      \n\n\n\n
      3. Hierarchical Inheritance<\/h3>\n\n\n\n
      In hierarchical inheritance, multiple subclasses extend from a single superclass. For example,<\/p>\n\n\n\n
      \"Both
      Java Hierarchical Inheritance<\/figcaption><\/figure>\n\n\n\n
      \n\n\n\n
      4. Multiple Inheritance<\/h3>\n\n\n\n
      In multiple inheritance, a single subclass extends from multiple superclasses. For example,<\/p>\n\n\n\n
      \"Class
      Java Multiple Inheritance<\/figcaption><\/figure>\n\n\n\n
      Note<\/strong>: Java doesn’t support multiple inheritance. However, we can achieve multiple inheritance using interfaces. <\/p>\n\n\n\n
      \n\n\n\n
      5. Hybrid Inheritance<\/h3>\n\n\n\n
      Hybrid inheritance is a combination of two or more types of inheritance. For example,<\/p>\n\n\n\n
      \"Class
      Java Hybrid Inheritance<\/figcaption><\/figure>\n\n\n\n
      Here, we have combined hierarchical and multiple inheritance to form a hybrid inheritance.<\/p>\n","protected":false},"excerpt":{"rendered":"
      In this tutorial, we will learn about Java inheritance and its types with the help of example. Inheritance is one of the key features of OOP that allows us to create a new class from an existing class. The new class that is created is known as subclass (child or derived class) and the existing class from […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[531],"tags":[],"_links":{"self":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/1202"}],"collection":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/comments?post=1202"}],"version-history":[{"count":0,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/1202\/revisions"}],"wp:attachment":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/media?parent=1202"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/categories?post=1202"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/tags?post=1202"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}