缓存不可变类实例的不可变类【参考疯狂Java讲义】

/**
 * 缓存实例的不可变类
 * @author RZL
 *
 */
public class ImmutaleCache {
	private static int MAX_SIZE = 10;
	private static ImmutaleCache[] cache = new ImmutaleCache[MAX_SIZE];
	private static int pos = 0;
	private final Person person;
	
	private ImmutaleCache(Person person){
		this.person = person;
	}
	
	public Person getPerson() {
		return person;
	}
	
	public static ImmutaleCache valueOf(Person person){
		//遍历已缓存的对象
		for(int i = 0; i < MAX_SIZE; i++){
			//如果已有相同实例，直接返回该缓存实例
			if(cache[i] != null && cache[i].getPerson().equals(person)){
				return cache[i];
			}
		}
		//如果缓存中没有且缓存已满
		if(pos >= MAX_SIZE){
			cache[0] = new ImmutaleCache(person);
			pos = 1;
		}else{
			cache[pos++] = new ImmutaleCache(person);
		}
		return cache[pos-1];
	}
	
	public boolean equals(Object obj) {
		if(this == obj){
			return true;
		}
		if(obj!= null && obj.getClass() == ImmutaleCache.class){
			ImmutaleCache ic = (ImmutaleCache)obj;
			return person.equals(ic.getPerson());
		}
		return false;
	}

	//重写hashCode方法是为了维护常规协议，该协议声明相等的对象具有相等的hash值
	public int hashCode() {
		return person.hashCode();
	}
	
	//........................main..............................
	public static void main(String[] args) {
		Name name1 = new Name("zhiliang","rui");
		Name name2 = new Name("zhiliang","rui");
		Person rzl = new Person(name1);
		Person me = new Person(name2);
		ImmutaleCache ic1 = ImmutaleCache.valueOf(rzl);
		ImmutaleCache ic2 = ImmutaleCache.valueOf(me);
		System.out.println(ic1==ic2);
		
	}
	//..........................................................
}

class Person {
	private final Name name;

	public Person(Name name) {
		//相当于值传递而不是引用传递，防止修改传入的Name对象而修改Person对象
		this.name = new Name(name.getFirstName(), name.getLastName());
	}

	public Name getName() {
		//返回一个匿名对象，该对象是原对象的一个副本，防止获取到Name对象引用后修改该对象而修改Person对象
		return new Name(name.getFirstName(), name.getLastName());
	}

	public boolean equals(Object object) {
		if (this == object) {
			return true;
		}
		if (object != null && object.getClass() == Person.class) {
			Person p = (Person) object;
			return name.equals(p.getName());
		}
		return false;
	}
	
	public int hashCode() {
		return name.hashCode();
	}
}

class Name {
	private String firstName;
	private String lastName;

	public Name() {
	}

	public Name(String firstName, String lastName) {
		this.firstName = firstName;
		this.lastName = lastName;
	}

	public String getFirstName() {
		return firstName;
	}

	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}

	public String getLastName() {
		return lastName;
	}

	public void setLastName(String lastName) {
		this.lastName = lastName;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		}
		if (obj != null && obj.getClass() == Name.class) {
			Name temp = (Name) obj;
			if (firstName.equals(temp.getFirstName())
					&& lastName.equals(temp.getLastName())) {
				return true;
			}
		}
		return false;
	}
	
	@Override
	public int hashCode() {
		return firstName.hashCode()+lastName.hashCode()*17;
	}
}