Provide a contract between a service provider and its clients.
An abstract class can provide implementation.
To make an abstract method, use the abstract modifier in front of the method declaration.
public abstract class DefaultPrinter {
public String toString() {
return "Use this to print documents.";
}
public abstract void print(Object document);
}
The toString method has an implementation, so you do not need to override this method.
The print method is declared abstract and does not have a body.
public class MyPrinter extends DefaultPrinter {
public void print(Object document) {
System.out.println("Printing document");
// some code here
}
}