Java Basics 1.12

Instance Methods

• Class method called from definition of the class
  • building up utility functions that pass all data in the call
  • STATIC present
• Instance method call from instance of the class - OBJECT
  • objects stick around and retain their data so its always accessible.
  • STATIC missing
• Method declarations
  • static - class method
  • public - called anywher ein ap
  • private - only within class
  • protected - only within this class or its subclasses

 

• Object Superclass methods with
• Olive()’s crush() method
• Olive inherits Object() methods/properties

 

Code: Main.java

package com.lynda.olivepress;

 

import com.lynda.olivepress.olives.Olive;

import com.lynda.olivepress.press.OlivePress;

 

public class Main {

    public static void main(String[] args) {

      //creating 3 anonymous Olive objects

      Olive[] olives = {new Olive(), new Olive(), new Olive()};

      OlivePress press = new OlivePress();

      press.getOil(olives);

    }

}

 

Code: OlivePress.java

package com.lynda.olivepress.press;

 

import com.lynda.olivepress.olives.Olive;

 

public class OlivePress {

    public void getOil(Olive[] olives)    {

      for (Olive olive : olives) {

            olive.crush();

      }

    }

}

Code: Olive.java

package com.lynda.olivepress.olives;

 

public class Olive {

   

    public void crush() {

      System.out.println("Ouch!");

    }

}

 

 

Instance Variables (Not Static)

 

Constructors

• Constructors have no return value (void, int, etc)
• can create multiple constructors (overloading) with different input specs
• Always create a ‘no argument’ constructor for clarity
  •                 public OlivePress() {    }
• Can Create a new constructor with fields....

 

 

 

 

 

Constructor of the Olive() class

     public Olive() {

      System.out.println("Constructor of " + this.name);

    }

 

Creating another constructor to catch argument and populate a field:

 

     public Olive(int oil) {

//this.oil means field(instance variable

//otherwise refers to argument

      this.oil = oil;

 

}

 

 

Code:

package com.lynda.olivepress.olives;

 

public class Olive {

   

    public String name = "Kalamata";

    public String flavor = "Grassy";

    public long color = 0x000000;

    private int oil = 3;

   

    //constructor, same name as class

    //no return on constructors

    //can overload the constructor

    public Olive() {

      System.out.println("Constructor of " + this.name);

    }

 

    public Olive(int oil) {

      this.oil = oil;

    }

 

    public int crush() {

      System.out.println("ouch!");

      return oil;

    }

}

 

 

Getters/Setters

• OO development patters
• Fields should be private
• Get to data with get/set
  • Create private get() and set()

 

Eclipse can create get/set code via Source:

 

 

Creates:

     public int getOil() {

      return oil;

    }

 

    public void setOil(int oil) {

      this.oil = oil;

    }

 

 

Code: Main.java

package com.lynda.olivepress;

 

import java.util.ArrayList;

 

import com.lynda.olivepress.olives.Olive;

import com.lynda.olivepress.press.OlivePress;

 

public class Main {

 

    public static void main(String[] args) {

      

      ArrayList<Olive> olives = new ArrayList<Olive>();

      

      Olive olive;

      

      olive = new Olive(2);

      System.out.println(olive.name);

      olives.add(olive);

 

      olive = new Olive(1);

      System.out.println(olive.name);

      olives.add(olive);

 

      olive = new Olive(2);

      System.out.println(olive.name);

      olives.add(olive);

   

      OlivePress press = new OlivePress();

      press.getOil(olives);

      System.out.println("You got " + press.getTotalOil() + " units of oil");

      

      press.getOil(olives);

      System.out.println("You got " + press.getTotalOil() + " units of oil");

    }

 

}

 

 

Code: OlivePress.java

package com.lynda.olivepress;

 

import java.util.ArrayList;

 

import com.lynda.olivepress.olives.Olive;

import com.lynda.olivepress.press.OlivePress;

 

public class Main {

 

    public static void main(String[] args) {

      

      ArrayList<Olive> olives = new ArrayList<Olive>();

      

      Olive olive;

      

      olive = new Olive(2);

      System.out.println(olive.name);

      olives.add(olive);

 

      olive = new Olive(1);

      System.out.println(olive.name);

      olives.add(olive);

 

      olive = new Olive(2);

      System.out.println(olive.name);

      olives.add(olive);

   

      OlivePress press = new OlivePress();

      press.getOil(olives);

      System.out.println("You got " + press.getTotalOil() + " units of oil");

      

      press.getOil(olives);

      System.out.println("You got " + press.getTotalOil() + " units of oil");

    }

 

}

 

 

Code: Olive.java

package com.lynda.olivepress;

 

import java.util.ArrayList;

 

import com.lynda.olivepress.olives.Olive;

import com.lynda.olivepress.press.OlivePress;

 

public class Main {

 

    public static void main(String[] args) {

      

      ArrayList<Olive> olives = new ArrayList<Olive>();

      

      Olive olive;

      

      olive = new Olive(2);

      System.out.println(olive.name);

      olives.add(olive);

 

      olive = new Olive(1);

      System.out.println(olive.name);

      olives.add(olive);

 

      olive = new Olive(2);

      System.out.println(olive.name);

      olives.add(olive);

   

      OlivePress press = new OlivePress();

      press.getOil(olives);

      System.out.println("You got " + press.getTotalOil() + " units of oil");

      

      press.getOil(olives);

      System.out.println("You got " + press.getTotalOil() + " units of oil");

    }

 

}