Java Tutorial/Design Pattern/Strategy Pattern

Action with the Strategy Pattern

public class MainClass {
  public static void main(String[] args) {
    Jet jet = new Jet();
    jet.setGoAlgorithm(new DriveEngine());
    jet.go();
    jet.setGoAlgorithm(new FlyFastEngine());
    jet.go();
    jet.setGoAlgorithm(new DriveEngine());
    jet.go();
  }
}
abstract class Vehicle {
  Engine goa = null;
  public Vehicle() {
  }
  void setGoAlgorithm(Engine goa) {
    this.goa = goa;
  }
  public void go() {
    this.goa.go();
  }
}
class Jet extends Vehicle {
  public Jet() {
  }
}
interface Engine {
  public void go();
}
class FlyingFastEngine implements Engine {
  public void go() {
    System.out.println("Now I"m flying fast.");
  }
}

class DriveEngine implements Engine {
  public void go() {
    System.out.println("Now I"m driving.");
  }
}

class FlyFastEngine implements Engine {
  public void go() {
    System.out.println("Now I"m flying fast.");
  }
}

Strategy: choosing the algorithm at run-time

interface Find {
  double[] algorithm(double[] line);
}
class FindMethodA implements Find {
  public double[] algorithm(double[] line) {
    return new double[] { 1 };
  }
}
class FindMethodB implements Find {
  public double[] algorithm(double[] line) {
    return new double[] { 2 };
  }
}
class FindMethodC implements Find {
  public double[] algorithm(double[] line) {
    return new double[] { 3 };
  }
}
class FindMethodD implements Find {
  public double[] algorithm(double[] line) {
    return new double[] { 4 };
  }
}
class MySolver {
  private Find strategy;
  public MySolver(Find strat) {
    strategy = strat;
  }
  double[] get(double[] line) {
    return strategy.algorithm(line);
  }
  void changeAlgorithm(Find newAlgorithm) {
    strategy = newAlgorithm;
  }
}
public class StrategyPattern {
  public static void main(String args[]) {
    MySolver solver = new MySolver(new FindMethodA());
    double[] line = { 1.0, 2.0, 1.0, 2.0, -1.0, 3.0, 4.0, 5.0, 4.0 };
    solver.get(line);
    solver.changeAlgorithm(new FindMethodC());
    solver.get(line);
  }
}