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;}@Overridepublic 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;}@Overridepublic int hashCode() {return firstName.hashCode()+lastName.hashCode()*17;}}