Prototaip dan Kumpulan Objek

class Configuration {
  String setting;
  public Configuration(String setting) {
    this.setting = setting;
  }
}

class Report implements Cloneable {
  String name;
  Configuration config;

  public Report(String name, Configuration config) {
    this.name = name;
    this.config = config;
  }

  @Override
  protected Object clone() throws CloneNotSupportedException {
    return super.clone(); // Shallow copy
  }

  public void display() {
    System.out.println("Report: " + name + ", Setting: " + config.setting);
  }
}

public class Main {
  public static void main(String[] args) {
    Configuration initialConfig = new Configuration("Default");
    Report originalReport = new Report("Monthly Sales", initialConfig);

    try {
      Report clonedReport = (Report) originalReport.clone();
      clonedReport.name = "Quarterly Sales";
      clonedReport.config.setting = "Aggregated"; // Changes original's config!

      originalReport.display();
      clonedReport.display();
    } catch (CloneNotSupportedException e) {
      e.printStackTrace();
    }
  }
}

class Configuration implements Cloneable {
  String setting;
  public Configuration(String setting) {
    this.setting = setting;
  }

  @Override
  protected Object clone() throws CloneNotSupportedException {
    return super.clone();
  }
}

class Report implements Cloneable {
  String name;
  Configuration config;

  public Report(String name, Configuration config) {
    this.name = name;
    this.config = config;
  }

  @Override
  protected Object clone() throws CloneNotSupportedException {
    Report cloned = (Report) super.clone();
    cloned.config = (Configuration) config.clone(); // Deep copy for config
    return cloned;
  }

  public void display() {
    System.out.println("Report: " + name + ", Setting: " + config.setting);
  }
}

public class Main {
  public static void main(String[] args) {
    Configuration initialConfig = new Configuration("Default");
    Report originalReport = new Report("Monthly Sales", initialConfig);

    try {
      Report clonedReport = (Report) originalReport.clone();
      clonedReport.name = "Quarterly Sales";
      clonedReport.config.setting = "Aggregated"; // Only changes cloned's config

      originalReport.display();
      clonedReport.display();
    } catch (CloneNotSupportedException e) {
      e.printStackTrace();
    }
  }
}

import java.util.ArrayList;
import java.util.List;

class DatabaseConnection {
  private int id;
  public DatabaseConnection(int id) {
    this.id = id;
    System.out.println("Connection " + id + " created.");
  }

  public void connect() {
    System.out.println("Connection " + id + " connected.");
  }
}

class ConnectionPool {
  private List<DatabaseConnection> availableConnections = new ArrayList<>();
  private List<DatabaseConnection> inUseConnections = new ArrayList<>();
  private int maxPoolSize;
  private int counter = 0;

  public ConnectionPool(int maxPoolSize) {
    this.maxPoolSize = maxPoolSize;
  }

  public synchronized DatabaseConnection acquireConnection() {
    if (availableConnections.isEmpty() && inUseConnections.size() < maxPoolSize) {
      DatabaseConnection newConn = new DatabaseConnection(++counter);
      inUseConnections.add(newConn);
      return newConn;
    } else if (!availableConnections.isEmpty()) {
      DatabaseConnection conn = availableConnections.remove(0);
      inUseConnections.add(conn);
      return conn;
    } else {
      System.out.println("Pool is full, no connections available.");
      return null; // Or wait, throw exception
    }
  }

  public synchronized void releaseConnection(DatabaseConnection connection) {
    if (connection != null && inUseConnections.remove(connection)) {
      availableConnections.add(connection);
      System.out.println("Connection " + connection.id + " released.");
    } else {
      System.out.println("Attempted to release unknown connection.");
    }
  }
}

public class Main {
  public static void main(String[] args) {
    ConnectionPool pool = new ConnectionPool(2);

    DatabaseConnection conn1 = pool.acquireConnection();
    if (conn1 != null) conn1.connect();

    DatabaseConnection conn2 = pool.acquireConnection();
    if (conn2 != null) conn2.connect();

    DatabaseConnection conn3 = pool.acquireConnection(); // Should say pool is full

    pool.releaseConnection(conn1);
    DatabaseConnection conn4 = pool.acquireConnection(); // Should reuse conn1
    if (conn4 != null) conn4.connect();
  }
}