Java Basics 1.16

Interfaces

• Allows definition of classes’ structure
  • final fields
  • method names
  • return data type
• Interfaces provides definition for creating classes
  • Allows for polymorphism due to similarities
• While <ArrayList> might be declared & used in the main logic,
  • helper classes can use Collection<T> so that other data types can be fed to it
  • such as
    • HashMap, Array, Enum
• Interfaces DON'T have constructors
  • good for modeling behavior
  • NOT for managing data
•  

Code:

This method only accept ArrayLists (part of Collection data type I/F)

public void getOil(ArrayList<Olive> olives) {}

 

This is more flexible and can take any Data Type that implements the Collection I/F

public void getOil(Collection<Olive> olives) {

 

Creating Interfaces

• No constructor methods or other class elements
• Modeling behavior, not dynamic managment of data
• MUST BE PUBLIC OR ABSTRACT
• Only include the METHOD SIGNATURE
•  

 

package com.lynda.olivepress.press;

 

public interface Press {

}

 

Creating a class with interface

 

Code:

package com.lynda.olivepress.press;

 

import java.util.Collection;

 

import com.lynda.olivepress.olives.Olive;

 

public class OlivePress2 implements Press {

 

    @Override

    public void getOil(Collection<Olive> olives) {

      // TODO Auto-generated method stub

 

    }

 

    @Override

    public int getTotalOil() {

      // TODO Auto-generated method stub

      return 0;

    }

 

    @Override

    public void setTotalOil(int totalOil) {

      // TODO Auto-generated method stub

    }

}