Interface
Interface can extend many interface.
Interface can extend from a interface only.
Interface have only abstract method by default.
Interface can have public method only it it.

Abstract
Abstract can attend only on class at a time.
Abstract class can extend from both abstact class and class.
A class can extend only one abstract class.
Abstract class can have both protected, private method.
Abstract Class

/* the Figure class must be declared as abstract 
   because it contains an abstract method  */

public abstract class Figure
{
    /* because this is an abstract method the 
       body will be blank  */
    public abstract float getArea();    
}

public class Circle extends Figure
{
    private float radius;

    public float getArea()
    {
        return (3.14 * (radius ^ 2));   
    }
}

public class Rectangle extends Figure
{
    private float length, width;

    public float getArea(Figure other)
    {
        return length * width;
    }
}

Interface

public interface Dog
{
    public boolean Barks();

    public boolean isGoldenRetriever();
}

Now, if a class were to implement this interface, this is what it would look like:

public class SomeClass implements Dog
{
    public boolean Barks{
    // method definition here

    }

    public boolean isGoldenRetriever{
    // method definition here
    }
}