Can a normal Class implement multiple interfaces

Question

I know that multiple inheritances between Interfaces is possible  e g    public interface C extends A B         Where A  B and C are Interfaces   But is it possible to have a regular Class inherit from multiple Interfaces like this   public class A implements C D         Where A is a Class and C and D are interfaces

User · Accepted Answer

A Java class can only extend one parent class. Multiple inheritance (extends) is not allowed. Interfaces are not classes, however, and a class can implement more than one interface.

The parent interfaces are declared in a comma-separated list, after the implements keyword.

In conclusion, yes, it is possible to do:

public class A implements C,D {...}

User · Answer

In a word - yes  Actually  many classes in the JDK implement multiple interfaces  E g   ArrayList implements List  RandomAccess  Cloneable  and Serializable

User · Answer

It is true that a java class can implement multiple interfaces at the same time  but there is a catch here  If in a class  you are trying to implement two java interfaces  which contains methods with same signature but diffrent return type  in that case you will get compilation error   interface One       int m1      interface Two       float m1      public class MyClass implements One  Two      int m1          float m1          public static void main String    args               output     prog java 14  error  method m1   is already defined in class MyClass     public float m1                         prog java 11  error  MyClass is not abstract and does not override abstract method m1   in Two public class MyClass implements One  Two           prog java 13  error  m1   in MyClass cannot implement m1   in Two     public int m1                         return type int is not compatible with float 3 errors

User · Answer

An interface can extend other interfaces  Also an interface cannot implement any other interface  When it comes to a class  it can extend one other class and implement any number of interfaces    class A extends B implements C D

User · Answer

public class A implements C D       valid   this is the way to implement multiple inheritence in java

User · Answer

Yes  it is possible  This is the catch  java does not support multiple inheritance  i e  class cannot extend more than one class  However class can implement multiple interfaces

User · Answer

Yes  a class can implement multiple interfaces  Each interface provides contract for some sort of behavior  I am attaching a detailed class diagram and shell interfaces and classes  Ceremonial example   public interface Mammal       void move        boolean possessIntelligence       public interface Animal extends Mammal       void liveInJungle        public interface Human extends Mammal  TwoLeggedMammal  Omnivore  Hunter       void liveInCivilization       public interface Carnivore       void eatMeat       public interface Herbivore       void eatPlant       public interface Omnivore extends Carnivore  Herbivore       void eatBothMeatAndPlant       public interface FourLeggedMammal       void moveWithFourLegs       public interface TwoLeggedMammal       void moveWithTwoLegs       public interface Hunter       void huntForFood       public class Kangaroo implements Animal  Herbivore  TwoLeggedMammal        Override     public void liveInJungle             System out println  quot I live in Outback country quot                Override     public void move             moveWithTwoLegs                Override     public void moveWithTwoLegs             System out println  quot I like to jump quot                Override     public void eat             eatPlant                Override     public void eatPlant             System out println  quot I like this grass quot                Override     public boolean possessIntelligence             return false            public class Lion implements Animal  FourLeggedMammal  Hunter  Carnivore        Override     public void liveInJungle             System out println  quot I am king of the jungle  quot                 Override     public void move             moveWithFourLegs                Override     public void moveWithFourLegs             System out println  quot I like to run sometimes  quot                Override     public void eat             eatMeat                Override     public void eatMeat             System out println  quot I like deer meat quot                Override     public boolean possessIntelligence             return false              Override     public void huntForFood             System out println  quot My females hunt often quot             public class Teacher implements Human        Override     public void liveInCivilization             System out println  quot I live in an apartment quot                Override     public void moveWithTwoLegs             System out println  quot I wear shoes and walk with two legs one in front of the other quot                Override     public void move             moveWithTwoLegs                Override     public boolean possessIntelligence             return true              Override     public void huntForFood             System out println  quot My ancestors used to but now I mostly rely on cattle quot                Override     public void eat             eatBothMeatAndPlant                Override     public void eatBothMeatAndPlant             eatPlant            eatMeat                Override     public void eatMeat             System out println  quot I like this bacon quot                Override     public void eatPlant             System out println  quot I like this broccoli quot

User · Answer

Of course    Almost all classes implements several interfaces  On any page of java documentation on Oracle you have a subsection named  All implemented interfaces     Here an example of the Date class

[java] Can a normal Class implement multiple interfaces?

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