标签：style class blog code java http
|
ReferenceQueue queue = new ReferenceQueue ();
PhantomReference pr = new PhantomReference (object, queue);
|
|
MyObject aRef = new MyObject();
SoftReference aSoftRef=new SoftReference(aRef);
|
|
aRef = null;
|
|
MyObject anotherRef=(MyObject)aSoftRef.get();
|
|
ReferenceQueue queue = new ReferenceQueue();
SoftReference ref=new SoftReference(aMyObject, queue);
|
|
SoftReference ref = null;
while ((ref = (EmployeeRef) q.poll()) != null) {
// 清除ref
}
|
|
public class Employee {
private String id;// 雇员的标识号码
private String name;// 雇员姓名
private String department;// 该雇员所在部门
private String Phone;// 该雇员联系电话
private int salary;// 该雇员薪资
private String origin;// 该雇员信息的来源
// 构造方法
public Employee(String id) {
this.id = id;
getDataFromlnfoCenter();
}
// 到数据库中取得雇员信息
private void getDataFromlnfoCenter() {
// 和数据库建立连接井查询该雇员的信息，将查询结果赋值
// 给name，department，plone，salary等变量
// 同时将origin赋值为"From DataBase"
}
……
|
|
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.util.Hashtable;
public class EmployeeCache {
static private EmployeeCache cache;// 一个Cache实例
private Hashtable<String,EmployeeRef> employeeRefs;// 用于Chche内容的存储
private ReferenceQueue<Employee> q;// 垃圾Reference的队列
// 继承SoftReference，使得每一个实例都具有可识别的标识。
// 并且该标识与其在HashMap内的key相同。
private class EmployeeRef extends SoftReference<Employee> {
private String _key = "";
public EmployeeRef(Employee em, ReferenceQueue<Employee> q) {
super(em, q);
_key = em.getID();
}
}
// 构建一个缓存器实例
private EmployeeCache() {
employeeRefs = new Hashtable<String,EmployeeRef>();
q = new ReferenceQueue<Employee>();
}
// 取得缓存器实例
public static EmployeeCache getInstance() {
if (cache == null) {
cache = new EmployeeCache();
}
return cache;
}
// 以软引用的方式对一个Employee对象的实例进行引用并保存该引用
private void cacheEmployee(Employee em) {
cleanCache();// 清除垃圾引用
EmployeeRef ref = new EmployeeRef(em, q);
employeeRefs.put(em.getID(), ref);
}
// 依据所指定的ID号，重新获取相应Employee对象的实例
public Employee getEmployee(String ID) {
Employee em = null;
// 缓存中是否有该Employee实例的软引用，如果有，从软引用中取得。
if (employeeRefs.containsKey(ID)) {
EmployeeRef ref = (EmployeeRef) employeeRefs.get(ID);
em = (Employee) ref.get();
}
// 如果没有软引用，或者从软引用中得到的实例是null，重新构建一个实例，
// 并保存对这个新建实例的软引用
if (em == null) {
em = new Employee(ID);
System.out.println("Retrieve From EmployeeInfoCenter. ID=" + ID);
this.cacheEmployee(em);
}
return em;
}
// 清除那些所软引用的Employee对象已经被回收的EmployeeRef对象
private void cleanCache() {
EmployeeRef ref = null;
while ((ref = (EmployeeRef) q.poll()) != null) {
employeeRefs.remove(ref._key);
}
}
// 清除Cache内的全部内容
public void clearCache() {
cleanCache();
employeeRefs.clear();
System.gc();
System.runFinalization();
}
}
|
|
public class SocketManager {
private Map<Socket, User> m = new HashMap<Socket, User>();
public void setUser(Socket s, User u) {
m.put(s, u);
}
public User getUser(Socket s) {
return m.get(s);
}
public void removeUser(Socket s) {
m.remove(s);
}
}
|
|
import java.util.WeakHashMap;
class Element {
private String ident;
public Element(String id) {
ident = id;
}
public String toString() {
return ident;
}
public int hashCode() {
return ident.hashCode();
}
public boolean equals(Object obj) {
return obj instanceof Element && ident.equals(((Element) obj).ident);
}
protected void finalize(){
System.out.println("Finalizing "+getClass().getSimpleName()+" "+ident);
}
}
class Key extends Element{
public Key(String id){
super(id);
}
}
class Value extends Element{
public Value (String id){
super(id);
}
}
public class CanonicalMapping {
public static void main(String[] args){
int size=1000;
Key[] keys=new Key[size];
WeakHashMap<Key,Value> map=new WeakHashMap<Key,Value>();
for(int i=0;i<size;i++){
Key k=new Key(Integer.toString(i));
Value v=new Value(Integer.toString(i));
if(i%3==0)
keys[i]=k;
map.put(k, v);
}
System.gc();
}
}
|
|
public class SocketManager {
private Map<Socket,User> m = new WeakHashMap<Socket,User>();
public void setUser(Socket s, User u) {
m.put(s, u);
}
public User getUser(Socket s) {
return m.get(s);
}
}
|
本文出自 “子 孑” 博客，请务必保留此出处http://zhangjunhd.blog.51cto.com/113473/53092
Java:对象的强、软、弱和虚引用(转),布布扣,bubuko.com
标签：style class blog code java http
原文地址：http://www.cnblogs.com/qq78292959/p/3799819.html
