Inheritance in Java

public class Person {
  public static final String STATE_DELIMITER = "~";
  public Person() {
    // Default constructor
  }
  public enum Gender {
    MALE,
    FEMALE,
   UNKNOWN
 }
  public Person(String name, int age, int height, int weight, String eyeColor, Gender gender) {
 this.name = name;
    this.age = age;
    this.height = height;
    this.weight = weight;
    this.eyeColor = eyeColor;
    this.gender = gender;
  }
 private String name;
 private int age;
 private int height;
 private int weight;
 private String eyeColor;
 private Gender gender;

The Person class in Listing 1 implicitly inherits from Object. Because inheriting from Object is assumed for every class, you don't need to type extends Object for every class you define. But what does it mean to say that a class inherits from its superclass? It simply means that Person has access to the exposed variables and methods in its superclasses. In this case, Person can see and use Object's public and protected methods and variables.

Why multiple inheritance is not supported in java?

To reduce the complexity and simplify the language, multiple inheritance is not supported in java.

Consider a scenario where A, B and C are three classes. The C class inherits A and B classes. If A and B classes have same method and you call it from child class object, there will be ambiguity to call method of A or B class.

Since compile time errors are better than runtime errors, java renders compile time error if you inherit 2 classes. So whether you have same method or different, there will be compile time error now.

class A{  
void msg(){System.out.println("Hello");}  
}  
class B{  
void msg(){System.out.println("Welcome");}

}  
class C extends A,B{//suppose if it were     
 Public Static void main(String args[]){  
   C obj=new C();  
  obj.msg();//Now which msg() method would be invoked?  
}  
}

class hierarchy

Now suppose you have an Employee class that inherits from Person. Employee's class definition would look something like this:

public class Employee extends Person {
 private String taxpayerIdentificationNumber;
 private String employeeNumber;
 private BigDecimal salary;

  // . . .
}

public class Manager extends Employee {
 // . . .
}