جاوا ۾ OOP تصورات

انڪپسوليشن

جاوا ۾ اهو ڪيئن ڪم ڪري ٿو:

1. زمينون ذاتي ڪيون وينديون آهن
2. ڪلاس ۾ هر فيلڊ کي ٻه خاص طريقا ملن ٿا: هڪ حاصل ڪندڙ ۽ هڪ سيٽر. حاصل ڪرڻ وارا طريقا فيلڊ جي قيمت واپس آڻيندا آھن. سيٽٽر طريقا توهان کي فيلڊ جي قيمت کي اڻ سڌي طرح پر جائز طريقي سان تبديل ڪرڻ جي اجازت ڏين ٿا.

جاوا ڪوڊ ۾ encapsulation جو مثال:

public class Student {
private int age;
private String name;

public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}

public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}

public class Test{
public static void main(String[] args) {
Student firstStudent = new Student();
firstStudent.setName("John");
// The name field is private, so you can no longer do this:  firstStudent.name = "John";
}
}

توهان کي encapsulation ڇو استعمال ڪرڻ گهرجي؟

public class HockeyStudent {
public String name;
public  int ageOfEnrollment;
}

وراثت

جاوا ۾ اهو ڪيئن ڪم ڪري ٿو:

1. والدين ڪلاس ٺاهيو.
2. Extensions keyword استعمال ڪندي ٻارن جو ڪلاس ٺاهيو .
3. چائلڊ ڪلاس جي ڪنسٽرڪٽر ۾، استعمال ڪريو super(parentField1, parentField2, ...) طريقو والدين جي فيلڊ کي سيٽ ڪرڻ لاءِ.

Student firstStudent = new Student();

ڪجهه ضابطا:

1. هڪ طبقي ۾ صرف هڪ والدين ٿي سگهي ٿو.
2. هڪ والدين طبقي جا ڪيترائي ٻار ڪلاس ٿي سگهن ٿا.
3. هڪ ٻار طبقو پنهنجو ٻار طبقو رکي سگهي ٿو.

جاوا ڪوڊ ۾ وراثت جو مثال

public class Phone {
    int price;
    double weight;

// Constructor
public Phone(int price, double weight) {
        this.price = price;
        this.weight = weight;
    }

    void orderPhone(){
        System.out.println("Ordering phone...");
    }
}

جاوا ۾ وراثت جو مثال

public class Android extends Phone {

// Some new fields
String androidVersion;
int screenSize;

    String secretDeviceCode;

// Constructor
    public Android(int price, double weight, String androidVersion, int screenSize, String secretDeviceCode) {
        super(price, weight); // Android inherits Phone’s fields

        //this - reference to the current object
        //super - reference to the parent object

        this.androidVersion = androidVersion;
        this.screenSize = screenSize;
        this.secretDeviceCode = secretDeviceCode;
    }

	// New Android-specific method, does not exist in the Phone class
    void installNewAndroidVersion() {
        System.out.println("installNewAndroidVersion invoked...");

    }

}

public class IPhone extends Phone {

    boolean fingerPrint;

    public IPhone(int price, double weight, boolean fingerPrint) {
        super(price, weight);
        System.out.println("IPhone constructor was invoked...");
        this.fingerPrint = fingerPrint;
    }

    void deleteIPhoneFromDb() {
        System.out.println("deleteIPhoneFromDb invoked...");
    }

@Override // This is about polymorphism, see below
void orderPhone(){
        System.out.println("Ordering my new iPhone and deleting the old one...");
    }
}

پوليمورفيزم

ان جو مطلب ڇا آهي ۽ اهو جاوا ۾ ڪيئن ڪم ڪري ٿو:

طريقه ڪار

جاوا ڪوڊ ۾ پوليمورفيزم جو مثال

public class Musician {
    String name;
    int age;

    // Default constructor
    public Musician() {
    }

    // Parameterized constructor
    public Musician(String name, int age) {
        this.name = name;
        this.age = age;
    }

    void play() {
        System.out.println("I am playing my instrument...");
    }
}

public class Pianist extends Musician {

    String favoritePianoType;

    public Pianist(String name, int age, String favoritePianoType) {
        super(name, age);
        this.favoritePianoType = favoritePianoType;
    }


    @Override
void play(){
        System.out.println("I am playing the piano...");
    }
}

public class Violinist extends Musician {
    boolean isSoloist;

public Violinist(String name, int age, boolean isSoloist) {
            super(name, age);
            this.isSoloist = isSoloist;
        }


    @Override
void play(){
if (isSoloist)
        System.out.println("I am playing the violin solo...");
else
System.out.println("I am playing the violin in an orchestra...");

    }
}

public class Demo {
  public static void main(String[] args) {
  Musician musician = new Musician();
  Violinist violinist = new Violinist("John", 32, true);
  Pianist pianist = new Pianist("Glen", 30, "Acoustic");

  System.out.println("Musician said:");
  musician.play();
  System.out.println("Violinist said:");
  violinist.play();
  System.out.println("Pianist said:");
  pianist.play();
    }
}

Musician said:
I am playing my instrument...
Violinist said:
I am playing the violin solo…
Pianist said:
I am playing the piano...

public class Pianist extends Musician {

    String favoritePianoType;

    @Override
    void play(){
        super.play();
        System.out.println("I am playing the piano...");
    }
}

Musician said:
I am playing my instrument...
Violinist said:
I am playing the violin solo...
Pianist said:
I am playing my instrument...
I am playing the piano...

اوور لوڊ ڪرڻ جو طريقو

public class Pianist extends Musician {

    String name;
    int age;
    String favoritePianoType;

    @Override
    void play(){
        super.play();
        System.out.println("I am playing the piano...");
    }
    void play(boolean isElectricity){
        if (isElectricity) {
            System.out.println("The electricity is on.");
            System.out.println("I am playing the piano...");
        }
        else System.out.println("I can't play this without electricity.");
    }
}

void play(boolean isElectricity){
        if (isElectricity) {
            System.out.println("The electricity is on.");
            play();
        }
        else System.out.println("I can't play this without electricity.");
    }

public class Demo {
    public static void main(String[] args) {

        Musician musician = new Musician();
        Violinist violinist = new Violinist("John", 23, true);
        Pianist pianist = new Pianist("Glen", 30, "Acoustic");

        System.out.println("Musician said:");
        musician.play();
        System.out.println("Violinist said:");
        violinist.play();
        System.out.println("Pianist said:");
        pianist.play();
        System.out.println("The pianist will now try the electric piano:");
        pianist.play(true);
        System.out.println("The electricity has been shut off. Now when trying the electric piano, the pianist says:");
        pianist.play(false);
    }
}

Musician said:
I am playing my instrument...
Violinist said:
I am playing the violin solo...
Pianist said:
I am playing my instrument...
I am playing the piano...
The pianist will now try the electric piano:
The electricity is on.
I am playing my instrument...
I am playing the piano...
The electricity has been shut off. Now when trying the electric piano, the pianist says:
I can't play this without electricity.

خلاصو

جاوا ۾ اهو ڪيئن ڪم ڪري ٿو:

1. تجريد جي هيٺين سطح هڪ مخصوص اعتراض آهي. اهو هڪ ادارو آهي جنهن جي خاصيتن جو هڪ سيٽ آهي جيڪو هڪ مخصوص طبقي سان تعلق رکي ٿو. اهو مخصوص فيلڊ قدر آهي

2. شيون ٺاهڻ لاءِ ٽيمپليٽ هڪ ڪلاس آهي. اهو هڪجهڙائي وارين ملڪيتن ۽ اندروني ڍانچي سان شين جي هڪ سيٽ جو بيان آهي.

3. خلاصو طبقو طبقن جي هڪ سيٽ جي خاصيتن جو خلاصو بيان آهي (اهو ٻين طبقن جي وراثت لاءِ ٽيمپليٽ طور ڪم ڪري ٿو). اهو هڪ اعلي سطحي تجريد آهي، تنهنڪري اهو ناممڪن آهي ته شيون سڌو سنئون تجريدي طبقي مان ٺاهيو وڃي. شيون ٺاهڻ لاءِ صرف خلاصي ڪلاس جا ٻار ڪلاس استعمال ڪري سگھجن ٿا. هڪ خلاصو طبقو شامل ٿي سگھي ٿو طريقن سان عمل درآمد سان، پر اهو گهربل ناهي.

4. هڪ انٽرفيس جاوا پروگرامنگ ٻولي جي تعمير جو هڪ تعمير آهي جنهن ۾ صرف خلاصي عوامي طريقا ۽ جامد مسلسل فيلڊ (فائنل جامد) شامل آهن. ٻين لفظن ۾، نه ئي تجريدي طبقن ۽ نه ئي انٽرفيس استعمال ڪري سگھجن ٿيون شيون پيدا ڪرڻ لاءِ.

جاوا ڪوڊ ۾ انٽرفيس جو مثال

interface Human {
	public void struggle();
	public void protect();
}

interface Vulcan {
	int angleOfPointyEars;
	public void turnOffEmotions(boolean isOn);
	public void telepathy();
}

The Spock class implements Human and Vulcan {
public void struggle() {
System.out.println("I am struggling...");
}
	public void protect() {
System.out.println("You are under my protection!”);
}
public void turnOffEmotions(boolean isOn){
If (isOn) {
System.out.println("I am turning off my emotions.");
isOn= !isOn;
}
}
	public void telepathy() {
System.out.println("Connecting to your brain...");
}

}