java classes implement interface code example

Example 1: java implement interface

// Assume we have the simple interface:
interface Appendable {
	void append(string content);
}
// We can implement it like that:
class SimplePrinter implements Appendable {
 	public void append(string content) {
   		System.out.println(content); 
    }
}
// ... and maybe like that:
class FileWriter implements Appendable {
 	public void append(string content) {
   		// Appends content into a file 
    }
}
// Both classes are Appendable.

Example 2: why we use interface in java

interface Animal {
   void child();
}
class Cat implements Animal {
   public void child() {
      System.out.println("kitten");
   }
}
class Dog implements Animal {
   public void child() {
      System.out.println("puppy");
   }
}
public class LooseCoupling{
   public static void main(String args[]) {
      Animal obj = new Cat();
      obj.child();
   }
}