Can a normal Class implement multiple interfaces?

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.

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 {...}

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

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

this is the way to implement multiple inheritence in java

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.

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{...}

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

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("I live in Outback country");
}


@Override
public void move() {
moveWithTwoLegs();
}


@Override
public void moveWithTwoLegs() {
System.out.println("I like to jump");
}


@Override
public void eat() {
eatPlant();
}


@Override
public void eatPlant() {
System.out.println("I like this grass");
}


@Override
public boolean possessIntelligence() {
return false;
}
}

public class Lion implements Animal, FourLeggedMammal, Hunter, Carnivore {
@Override
public void liveInJungle() {
System.out.println("I am king of the jungle!");


}


@Override
public void move() {
moveWithFourLegs();
}


@Override
public void moveWithFourLegs() {
System.out.println("I like to run sometimes.");
}


@Override
public void eat() {
eatMeat();
}


@Override
public void eatMeat() {
System.out.println("I like deer meat");
}


@Override
public boolean possessIntelligence() {
return false;
}


@Override
public void huntForFood() {
System.out.println("My females hunt often");
}
}

public class Teacher implements Human {
@Override
public void liveInCivilization() {
System.out.println("I live in an apartment");
}


@Override
public void moveWithTwoLegs() {
System.out.println("I wear shoes and walk with two legs one in front of the other");
}


@Override
public void move() {
moveWithTwoLegs();
}


@Override
public boolean possessIntelligence() {
return true;
}


@Override
public void huntForFood() {
System.out.println("My ancestors used to but now I mostly rely on cattle");
}


@Override
public void eat() {
eatBothMeatAndPlant();
}


@Override
public void eatBothMeatAndPlant() {
eatPlant();
eatMeat();
}


@Override
public void eatMeat() {
System.out.println("I like this bacon");
}


@Override
public void eatPlant() {
System.out.println("I like this broccoli");
}
}