SaBenBurra

public interface IPushNotificationService {

  public boolean sendNotificationToSingleUser(String data, String clientId);
  public boolean sendNotificationToAllUsers(String data);
}

SaBenBurra

public class Main {
  public static void main(String[] args) {
    FirebasePushNotification notificationService = new FirebasePushNotification();
    
    notificationService.sendNotificationToSingleUser("Hello", "123456");
    notificationService.sendNotificationToAllUsers("Hello world");
    
    //...
    notificationService.sendNotificationToSingleUser("Hello", "123456");
    notificationService.sendNotificationToAllUsers("Hello world");

SaBenBurra

public class FirebasePushNotification {
  public boolean sendNotificationToSingleUser(String data, String clientId) {
    //işlemler 
  }
  
  public boolean sendNotificationToAllUsers(String data) {
    //işlemler
  }
}

SaBenBurra

public class Main {
  public void main(String[] args) {
    SampleClass myObject1 = new SampleClass(5);
    SampleClass myObject2 = myObject1;
    myObject2.number = 20;
    System.out.println(myObject1.number);
  }
}

SaBenBurra

public class SampleClass {
  int number;
  public SampleClass(int number) {
    this.number = number;
  }
}

SaBenBurra

public class Main {
  public static void main(String[] args) {
    int number1 = 5;
    int number2 = 10;
    number1 = number2;
    number2 = 15;
    System.out.println(number1);
  }
}