import java.util.*;abstract class Shape {void draw() { System.out.println(this + ".draw()"); }abstract public String toString();
}class Circle extends Shape {public String toString() { return "Circle"; }
}class Square extends Shape {public String toString() { return "Square"; }
}class Triangle extends Shape {public String toString() { return "Triangle"; }
}public class Shapes {public static void main(String[] args){List<Shape> shapeList = Arrays.asList(new Circle(), new Square(), new Triangle());for(Shape shape : shapeList)shape.draw();}
} /* Output:
Circle.draw()
Square.draw()
Triangle.draw()
*/

// Examination of the way the class loader works.
import static net.mindview.util.Print.*;class Candy {static { print("Loading Candy"); }
}class Gum {static { print("Loading Gum"); }
}class Cookie {static { print("Loading Cookie"); }
}public class SweetShop {public static void main(String[] args){print("inside main");new Candy();print("After creating Candy");try {Class.forName("Gum");} catch(ClassNotFoundException e){print("Couldn't find Gum");}print("After Class.forName(\"Gum\")");new Cookie();print("After creating Cookie");}
} /* Output:
inside main
Loading Candy
After creating Candy
Loading Gum
After Class.forName("Gum")
Loading Cookie
After creating Cookie
*/

// Testing Class Class.
package Leetcode.DrJava;
import static net.mindview.util.Print.*;interface HasBatteries {}
interface Waterproof {}
interface Shoots {}class Toy {// Comment out the following default constructor// to see NoSuchMethodError from (*1*)Toy() {}Toy(int i) {}
}class FancyToy extends Toy implements HasBatteries, Waterproof, Shoots {FancyToy() { super(1); }
}public class ToyTest {static void printInfo(Class cc){print("Class name: " + cc.getName() + " is interface? [" + cc.isInterface() + "]");print("Simple name: " + cc.getSimpleName());print("Canonical name: " + cc.getCanonicalName());}public static void main(String[] args){Class c = null;// get the reference of a Class try {c = Class.forName("Leetcode.DrJava.FancyToy");} catch(ClassNotFoundException e){print("Can't find FancyToy");System.exit(1);}        printInfo(c);// return the interfaces in "c" Class.for(Class face : c.getInterfaces())printInfo(face);// return the superclass of the "c" classClass up = c.getSuperclass();Object obj = null;        try {// Requires default constructorobj = up.newInstance();} catch(InstantiationException e){print("Cannot instantiate");System.exit(1);} catch(IllegalAccessException e){print("Can't access");System.exit(1);}      printInfo(obj.getClass());      }
} /* Output:
Class name: Leetcode.DrJava.FancyToy is interface? [false]
Simple name: FancyToy
Canonical name: Leetcode.DrJava.FancyToy
Class name: Leetcode.DrJava.HasBatteries is interface? [true]
Simple name: HasBatteries
Canonical name: Leetcode.DrJava.HasBatteries
Class name: Leetcode.DrJava.Waterproof is interface? [true]
Simple name: Waterproof
Canonical name: Leetcode.DrJava.Waterproof
Class name: Leetcode.DrJava.Shoots is interface? [true]
Simple name: Shoots
Canonical name: Leetcode.DrJava.Shoots
Class name: Leetcode.DrJava.Toy is interface? [false]
Simple name: Toy
Canonical name: Leetcode.DrJava.Toy
*/

FancyToy.class

import java.util.*;class Initable {static final int staticFinal = 47;static final int staticFinal2 = ClassInitialization.rand.nextInt(1000);    static {System.out.println("Initializing Initable");}
}class Initable2 {static int staticNonFinal = 147;static {System.out.println("Initializing Initable2");}
}class Initable3 {static int staticNonFinal = 74;static {System.out.println("Initializing Initable3");}
}public class ClassInitialization {public static Random rand = new Random(47);public static void main(String[] args) throws Exception {Class initable = Initable.class;System.out.println("After creating Initable ref");// Does not trigger initialization:System.out.println(Initable.staticFinal);// Does not trigger initialization:System.out.println(Initable.staticFinal2);// Does not trigger initialization:System.out.println(Initable2.staticNonFinal);Class initable3 = Class.forName("Initable3");System.out.println("After creating Initable3 ref");System.out.println(Initable3.staticNonFinal);}
} /* Output:
After creating Initable ref
47
Initializing Initable
258
Initializing Initable2
147
Initializing Initable3
After creating Initable3 ref
74
*/