1.策略 ：定义不同的

2. 例子：随机生成宠物，并统计各种宠物生成数量。

a) 抽象类：PetCreator，用于随机生成宠物。

package context;

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

import java.util.Random;

public abstract class PetCreator {

private Random rand = new Random(47);

//抽象接口，策略模式，子类实现具体策略

public abstract List> getTypes();

public Pet randomPet() {

int n = rand.nextInt(getTypes().size());

try {

return getTypes().get(n).newInstance();

} catch (InstantiationException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

e.printStackTrace();

}

return null;

}

public Pet[] createArray(int size) {

Pet[] result = new Pet[size];

for(int i=0; i

result[i] = randomPet();

}

return result;

}

public List createList(int size) {

List result = new ArrayList();

Collections.addAll(result, createArray(size));

return result;

}

}

b) 策略1：依据字符串生成宠物类型

package context;

import java.util.ArrayList;

import java.util.List;

public class ForNameCreator extends PetCreator {

private static List> types = new ArrayList>();

private static String[] typeNames = {

"context.Pet",

"context.Cat",

"context.Dog",

"context.Rodent",

"context.MUTT",

"context.PUG",

"context.Manx",

"context.EgyptianMau",

"context.Cymric",

"context.Rat",

"context.Mouse",

"context.Hamster"

};

@SuppressWarnings("unchecked")

private static void loader() {

try {

for(String name : typeNames) {

types.add((Class extends Pet>) Class.forName(name));

}

} catch (ClassNotFoundException e) {

e.printStackTrace();

}

}

static {

loader();

}

@Override

public List> getTypes() {

return types;

}

}

c) 策略2：依据class生成宠物类型

package context;

import java.util.Arrays;

import java.util.Collections;

import java.util.List;

public class LiteralPetCreator extends PetCreator {

@SuppressWarnings("unchecked")

public static final List> allType = Collections.unmodifiableList(Arrays.asList(

Pet.class, Dog.class, Cat.class, Rodent.class, MUTT.class, PUG.class, Manx.class,

EgyptianMau.class, Cymric.class, Rat.class, Mouse.class, Hamster.class));

private static final List> types = allType.subList(allType.indexOf(MUTT.class), allType.size());

@Override

public List> getTypes() {

return types;

}

}

d) 计数器：统计随机生成的宠物数量

package context;

import java.util.HashMap;

public class PetCount {

static class PetConter extends HashMap {

private static final long serialVersionUID = 1L;

public void count(String type) {

Integer num = get(type);

if(null == num) {

put(type, 1);

} else {

put(type, num + 1);

}

}

}

public static void countPet(PetCreator petCreator) {

PetConter petConter = new PetConter();

for(Pet pet : petCreator.createArray(20)) {

System.out.print(pet.getClass().getSimpleName() + " ");

if(pet instanceof MUTT) {

petConter.count("MUTT");

}

if(pet instanceof PUG) {

petConter.count("PUG");

}

if(pet instanceof EgyptianMau) {

petConter.count("EgyptianMau");

}

if(pet instanceof Cymric) {

petConter.count("Cymric");

}

if(pet instanceof Manx) {

petConter.count("Manx");

}

if(pet instanceof Rat) {

petConter.count("Rat");

}

if(pet instanceof Mouse) {

petConter.count("Mouse");

}

if(pet instanceof Hamster) {

petConter.count("Hamster");

}

if(pet instanceof Rodent) {

petConter.count("Rodent");

}

if(pet instanceof Dog) {

petConter.count("Dog");

}

if(pet instanceof Cat) {

petConter.count("Cat");

}

if(pet instanceof Pet) {

petConter.count("Pet");

}

}

System.out.println();

System.out.println(petConter);

}

public static void main(String[] args) {

//PetCount.countPet(new ForNameCreator());

PetCount.countPet(Pets.creator);

}

}

e) 外观实现：将策略2定义为默认实现

package context;

import java.util.List;

public class Pets {

public static final PetCreator creator = new LiteralPetCreator(); //外观模式

public static Pet randomPet() {

return creator.randomPet();

}

public static Pet[] createArray(int size) {

return creator.createArray(size);

}

public static List createList(int size) {

return creator.createList(size);

}

}

f) 宠物类：

package context;

public class Pet {

private String name;

public Pet() {

super();

}

public Pet(String name) {

super();

this.name = name;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

}

class Dog extends Pet {

public Dog() {

super();

}

public Dog(String name) {

super();

}

}

class MUTT extends Dog {

public MUTT() {

super();

}

public MUTT(String name) {

super(name);

}

}

class PUG extends Dog {

public PUG() {

super();

}

public PUG(String name) {

super(name);

}

}

class Cat extends Pet {

public Cat() {

super();

}

public Cat(String name) {

super(name);

}

}

class Manx extends Cat {

public Manx() {

super();

}

public Manx(String name) {

super(name);

}

}

class EgyptianMau extends Cat {

public EgyptianMau() {

super();

}

public EgyptianMau(String name) {

super(name);

}

}

class Cymric extends Manx {

public Cymric() {

super();

}

public Cymric(String name) {

super(name);

}

}

class Rodent extends Pet {

public Rodent() {

super();

}

public Rodent(String name) {

super(name);

}

}

class Rat extends Rodent {

public Rat() {

super();

}

public Rat(String name) {

super(name);

}

}

class Mouse extends Rodent {

public Mouse() {

super();

}

public Mouse(String name) {

super(name);

}

}

class Hamster extends Rodent {

public Hamster() {

super();

}

public Hamster(String name) {

super(name);

}

}