A subclass in Java is a class that inherits methods and values from the superclass. It is the child class. It can have methods and values of its own aside from possessing all the variables.<\/p>\n
Java Superclass<\/strong><\/p>\n A superclass in Java is a class from which the child class inherits all the methods and values. This is the parent class.<\/p>\n Syntax for defining inheritance between two classes:<\/strong><\/p>\n <child class> extends <parent-class><\/strong><\/p>\n Inheritance allows programmers to define a class in terms of another class, which enhances code readability and interpretability. This helps in the maintenance of the application. We can also reuse the code from the parent class and override it according to the needs of the program.<\/p>\n The extends keyword extends the functionality of the child class by inheriting values from the parent class. It defines an \u201cis-a\u201d relationship. It comes after the class definition and carries the class name of the parent class. The syntax is as follows<\/p>\n <child class> extends <parent-class><\/strong><\/p>\n This means that the child class is a type of parent class.<\/p>\n There are two types of relationships in Java. They are as follows: An \u201cis-a\u201d relationship gets implemented by inheritance. This means that a certain class is a part of the parent class. This is essential for code reusability. Inheritance is unidirectional, which means that the child class is a type of parent class, but the inverse is not true. For example, a brush is a tool, but not all tools are brushes. This relationship gets implemented with the help of extends and implements keywords.<\/p>\n Composition is the other word of the \u201chas-a\u201d relationship. It means that a certain instance of this class has a reference to another class or is in the same class. This relationship also helps in code reusability.<\/p>\n For example, A square has edges, A brush has bristles, and a cat has a tail. This implementation is possible if we use the new keyword.<\/p>\n Inheritance offers several advantages in object-oriented programming:<\/p>\n 1. Code Reusability:<\/strong> By inheriting properties and behaviors from a parent class, you can avoid duplicating code. This promotes code maintainability and reduces the chances of errors.<\/p>\n 2. Extensibility:<\/strong> Inheritance allows you to create specialized subclasses that extend the functionality of a parent class. This is particularly useful for building hierarchies of related classes.<\/p>\n 3. Polymorphism:<\/strong> Inheritance enables polymorphic behavior, where subclasses can redefine methods inherited from the parent class. This allows you to write flexible code that can work with objects of different types.<\/p>\n Java supports the following kinds of interfaces: In single inheritance, a single child class inherits data and methods from its parent class. In this case, a child class can access all the methods and the variables of the parent class.<\/p>\n This diagram illustrates a single inheritance where class B inherits from class A.<\/p>\n Java program to illustrate Single Inheritance:<\/strong><\/p>\n Output:<\/strong><\/p>\n This represents a multi-tier inheritance wherein the child class inherits from a parent class, which in itself is a child class of another parent class.\u00a0It is created when a single level contains more levels of inheritance. In multilevel inheritance, the child class at the end will have all the properties of the first parent class. A real-life example would be a child inheriting from his father, who inherited from his grandfather<\/p>\n This is an example of a multilevel inheritance where C inherits from B and B inherits from A.<\/p>\n Java program to illustrate the use of Multilevel Inheritance:<\/strong><\/p>\n Output:<\/strong><\/p>\n As you can see, when the base class is declared and when the object gets created, it calls the constructor of the base class. However, its parent class\u2019s constructor gets executed first. This is an important concept to understand.<\/p>\n In this type of inheritance, a single parent class passes its values and methods to multiple child classes. One class serves as the parent class, and the rest of the classes are the child classes.<\/p>\n It has a tree-like structure in which a parent class can have more than one child class, and it can go further. Whereas the super class at the top represents the root, and other sub-classes are referred to as branches.<\/p>\n This is an example of hierarchical inheritance where classes B and C inherit from parent class A.<\/p>\n Java program to illustrate Hierarchical Inheritance:<\/strong><\/p>\n Output:<\/p>\n Multiple Inheritance, as the name suggests, means that multiple child classes can derive from one parent class. It is not allowed in Java. However, it can be implemented by using Interfaces.<\/p>\nWhy do we need Inheritance in Java?<\/h3>\n
extends Keyword in Java<\/h3>\n
Types of relationships in Java<\/h3>\n
\n1.<\/strong> \u201cis-a\u201d relationship
\n2.<\/strong> \u201cHas-a\u201d relationship<\/p>\nJava \u201cis-a\u201d relationship<\/h4>\n
Java \u201chas-a\u201d relationship<\/h4>\n
Benefits of Inheritance in Java<\/h4>\n
Different Types of Inheritance in Java<\/h3>\n
![\"Types](\"https:\/\/data-flair.training\/blogs\/wp-content\/uploads\/sites\/2\/2018\/02\/Types-of-Inheritance-in-Java-1.jpg\")
<\/a><\/p>\n
\na.<\/strong> Single Inheritance
\nb.<\/strong> Multilevel Inheritance
\nc.<\/strong> Hierarchical Inheritance
\nd.<\/strong> Multiple Inheritance(Only through Interfaces)
\ne.<\/strong> Hybrid Inheritance<\/p>\nSingle Inheritance in Java<\/h4>\n
<\/a><\/p>\npackage com.dataflair.javainheritance;\r\nclass Father {\r\n String familyName;\r\n String houseaddress;\r\n Father() {\r\n familyName = \"Programmer\";\r\n houseaddress = \"Delhi\";\r\n }\r\n}\r\npublic class Son extends Father {\r\n String name;\r\n Son() {\r\n name = \"Shraman\";\r\n }\r\n void printdetails() {\r\n System.out.println(\"Hey my name is \" + this.name + \" \" + this.familyName + \" and I am from \" + this.houseaddress);\r\n }\r\n public static void main(String[] args) {\r\n Son s1 = new Son();\r\n s1.printdetails();\r\n\r\n }\r\n}<\/pre>\nMultilevel Inheritance in Java<\/h4>\n
<\/a><\/p>\npackage com.dataflair.javainheritance;\r\nclass GrandFather {\r\n GrandFather() {\r\n System.out.println(\"I am the grandfather!\");\r\n }\r\n}\r\n\r\nclass Father extends GrandFather {\r\n String familyName;\r\n String houseaddress;\r\n Father() {\r\n System.out.println(\"I am the father! I inherit from Grandfather\");\r\n }\r\n}\r\npublic class Son extends Father {\r\n\r\n Son() {\r\n System.out.println(\"I am the son and I inherit from my father.\");\r\n }\r\n\r\n public static void main(String[] args) {\r\n Son s1 = new Son();\r\n\r\n }\r\n}<\/pre>\n
\nI am the father! I inherit from Grandfather
\nI am the son and I inherit from my father.<\/div>\nHierarchical Inheritance in Java<\/h4>\n
<\/a><\/p>\npackage com.dataflair.javainheritance;\r\nclass Father {\r\n String familyName;\r\n String houseaddress;\r\n Father() {\r\n familyName = \"Programmer\";\r\n houseaddress = \"Delhi\";\r\n }\r\n}\r\nclass Son extends Father {\r\n Son() {\r\n System.out.println(\"I am the Son\");\r\n System.out.println(\"My family name is \" + this.familyName + \" and I am from \" + this.houseaddress);\r\n\r\n }\r\n\r\n}\r\nclass Daughter extends Father {\r\n Daughter() {\r\n System.out.println(\"I am the Daughter\");\r\n System.out.println(\"My family name is \" + this.familyName + \" and I am from \" + this.houseaddress);\r\n }\r\n}\r\nclass Main {\r\n public static void main(String[] args) {\r\n Son s = new Son();\r\n Daughter d = new Daughter();\r\n }\r\n}<\/pre>\n
\nMy family name is Programmer and I am from Delhi
\nI am the Daughter
\nMy family name is Programmer and I am from Delhi<\/div>\nMultiple Inheritance in Java<\/h4>\n