App.java

/**
 * The MIT License
 * Copyright (c) 2014-2016 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package com.iluwatar.delegation.simple;

import com.iluwatar.delegation.simple.printers.CanonPrinter;
import com.iluwatar.delegation.simple.printers.EpsonPrinter;
import com.iluwatar.delegation.simple.printers.HpPrinter;

/**
 * The delegate pattern provides a mechanism to abstract away the implementation and control of the desired action.
 * The class being called in this case {@link PrinterController} is not responsible for the actual desired action,
 * but is actually delegated to a helper class either {@link CanonPrinter}, {@link EpsonPrinter} or {@link HpPrinter}.
 * The consumer does not have or require knowledge of the actual class carrying out the action, only the
 * container on which they are calling.
 *
 * In this example the delegates are {@link EpsonPrinter}, {@link HpPrinter} and {@link CanonPrinter} they all implement
 * {@link Printer}. The {@link PrinterController} class also implements {@link Printer}. However neither provide the
 * functionality of {@link Printer} by printing to the screen, they actually call upon the instance of {@link Printer}
 * that they were instantiated with. Therefore delegating the behaviour to another class.
 */
public class App {

  public static final String MESSAGE_TO_PRINT = "hello world";

  /**
   * Program entry point
   *
   * @param args command line args
   */
  public static void main(String[] args) {
    PrinterController hpPrinterController = new PrinterController(new HpPrinter());
    PrinterController canonPrinterController = new PrinterController(new CanonPrinter());
    PrinterController epsonPrinterController = new PrinterController(new EpsonPrinter());

    hpPrinterController.print(MESSAGE_TO_PRINT);
    canonPrinterController.print(MESSAGE_TO_PRINT);
    epsonPrinterController.print(MESSAGE_TO_PRINT);
  }

}