How does interfaces overcome the problem of single inheritance?

Question

1) How does interfaces overcome the problem of single inheritance? Can anyone give an example of how it works?
2) In a Java book, I read: "Interfaces are implemented and used throughout the Java class library when behavior is expected to be implemented by a number of disparate classes."
Why does different classes require to implement a Java class library?
Can anyone please enlighten? Thanks.

Answer 1

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2) In a Java book, I read: "Interfaces are implemented and used throughout the Java class library when behavior is expected to be implemented by a number of disparate classes."
Hi, let me try to explain this.
Say you have a left hand drive BMW and a right hand drive AUDI. typeOfDrive is a property for these two cars. If i am trying to make this property abstract, i will prefer to put this property in an Interface called Car. My classes BmwCar and AudiCar implement the Car Interface; by which they can use the property typeOfDrive.
So, the behaviour 'typeOfDrive'; when expected to be implemented by Disparate entities BmwCar and AudiCar, we try to abstract that property to a common Interface called Car.
interface Car {
String typeOfDrive;
String getTypeOfDrive();
class BmwCar implements Car {
String getTypeOfDrive() {
   return typeOfDrive;
void setTypeOfDrive(String tod) {
this.typeOfDrive = tod;
class AudiCar implements Car {
String getTypeOfDrive() {
   return typeOfDrive;
void setTypeOfDrive(String tod) {
this.typeOfDrive = tod;
}Now, when you create instance of your disparate classes, you will define the declared property 'typeOfDrive', as 'Left Hand Drive' for BmwCar and 'Right Hand Drive' for AudiCar.
So, "Interfaces are implemented and used throughout the Java class library when behavior is expected to be implemented by a number of disparate classes."
You can refer to many web wikis for better examples and explanations.
Regards,
~N~