gistfile1.txt

interface DatabaseExecuter {
  public void executeDatabase(String query);
}

class DatabaseExecuterImpl implements DatabaseExecuter {

  @Override
  public void executeDatabase(String query) {
    System.out.println("Going to execute Query: " + query);
  }
  
}

class DatabaseExecuterProxy implements DatabaseExecuter {
  boolean ifAdmin;
  DatabaseExecuterImpl dbExecuter;
  
  public DatabaseExecuterProxy(String name, String passwd) {
    if(name == "Admin" && passwd == "Admin@123") {
      ifAdmin = true;
    }
    dbExecuter = new DatabaseExecuterImpl();
  }

  @Override
  public void executeDatabase(String query) throws Exception {
    if(ifAdmin) {
      dbExecuter.executeDatabase(query);
    } else {
      if(query.equals("DELETE")) {
        throw new Exception("DELETE not allowed for non-admin user");
      } else {
        dbExecuter.executeDatabase(query);
      }
    }
  }
}

public class ProxyPatternExample {

  public static void main(String[] args) throws Exception {
    DatabaseExecuter nonAdminExecuter = new DatabaseExecuterProxy("NonAdmin", "Admin@123");
    nonAdminExecuter.executeDatabase("DELEE");
    
    DatabaseExecuter nonAdminExecuterDELETE = new DatabaseExecuterProxy("NonAdmin", "Admin@123");
    nonAdminExecuterDELETE.executeDatabase("DELETE");

    
    DatabaseExecuter adminExecuter = new DatabaseExecuterProxy("Admin", "Admin@123");
    adminExecuter.executeDatabase("DELETE");
    
  }

}