Java缓存池代码实例详解

package com.paic.zhangqi.cache;  import java.util.Date;  /**  * 缓存实体  * @author ZHANGQI947  */ public class CacheItem {   // 创建缓存时间  private Date createTime = new Date();    // 缓存期满时间  private long expireTime = 1;    // 缓存实体  private Object entity;     public CacheItem(Object obj, long expires) {   this.entity = obj;   this.expireTime = expires;  }    // 判断缓存是否超时  public boolean isExpired() {   return (expireTime != -1 && new Date().getTime() - createTime.getTime() > expireTime);  }   public Date getCreateTime() {   return createTime;  }   public void setCreateTime(Date createTime) {   this.createTime = createTime;  }   public Object getEntity() {   return entity;  }   public void setEntity(Object entity) {   this.entity = entity;  }   public long getExpireTime() {   return expireTime;  }   public void setExpireTime(long expireTime) {   this.expireTime = expireTime;  } } 

package com.paic.zhangqi.cache;  import java.util.Date; import java.util.HashMap; import java.util.Map; /**  * 缓存池  * @author Administrator  */ public class CachePool {  // 缓存池唯一实例  private static CachePool instance;  // 缓存Map  private static Map<String, Object> cacheItems;    private CachePool() {   cacheItems = new HashMap<String, Object>();  }    /**   * 获取唯一的实例   * @return instance   */  public synchronized static CachePool getInstance() {   if (instance == null) {    instance = new CachePool();   }   return instance;  }    /**   * 清除所有的Item缓存   */  public synchronized void clearAllItems() {   cacheItems.clear();  }    /**   * 获取缓存实例   * @param name 缓存名称   * @return 缓存实例   */  public synchronized Object getCacheItem(String name) {   if (!cacheItems.containsKey(name)) {    return null;   }   CacheItem cacheItem = (CacheItem) cacheItems.get(name);   if (cacheItem.isExpired()) {    return null;   }   return cacheItem.getEntity();  }  /**   * 存放缓存信息   * @param name 名称   * @param obj 实例对象   * @param expires 超时时长   */  public synchronized void putCacheItem(String name, Object obj, long expires) {   // 判断该对象是否在在缓存池，不在直接put   if (!cacheItems.containsKey(name)) {    cacheItems.put(name, new CacheItem(obj, expires));   }   // 获取缓存池中对象，更新对象信息   CacheItem cacheItem = (CacheItem) cacheItems.get(name);   cacheItem.setCreateTime(new Date());   cacheItem.setEntity(obj);   cacheItem.setExpireTime(expires);  }  /**   * 移除缓存数据   * @param name   */  public synchronized void removeCacheItem(String name) {   if (!cacheItems.containsKey(name)) {    return ;   }   cacheItems.remove(name);  }    /**   * 获取缓存数据的数量   * @return   */  public int getSize() {   return cacheItems.size();  }  } 

package com.paic.zhangqi.cache; /**  * 学生类  * @author Administrator  */ public class Student {   private String name;  private String id;  private int age;  private int sal;  public Student() {     }    public Student(String name, String id, int age, int sal) {   this.name = name;   this.id = id;   this.age = age;   this.sal = sal;  }   public String getName() {   return name;  }   public void setName(String name) {   this.name = name;  }   public String getId() {   return id;  }   public void setId(String id) {   this.id = id;  }   public int getAge() {   return age;  }   public void setAge(int age) {   this.age = age;  }   public int getSal() {   return sal;  }  public void setSal(int sal) {   this.sal = sal;  } }

package com.paic.zhangqi.cache; /**  * 主测试类  * @author ZHANGQI947  */ public class MainTest {   /**   * @param args   * @throws InterruptedException   */  public static void main(String[] args) throws InterruptedException {   // 获取缓存池   CachePool cachePool = CachePool.getInstance();      Student stu1 = new Student("l1", "stu001", 25, 40);   Student stu2 = new Student("l2", "stu002", 25, 40);   Student stu3 = new Student("l3", "stu003", 25, 40);   Student stu4 = new Student("l4", "stu004", 25, 40);      cachePool.putCacheItem("001", stu1, 122222);   cachePool.putCacheItem("002", stu2, 10);   cachePool.putCacheItem("003", stu3, 360002);   cachePool.putCacheItem("004", stu4, 1222222);      // 设置线程休眠，其中002对象会超时   Thread.sleep(200);      Student stu001 = (Student) cachePool.getCacheItem("001");   if (null != stu001) {    System.out.println(stu001.getName());   }      // 由于超时，这里取出的002对象为null   Student stu002 = (Student) cachePool.getCacheItem("002");   if (null != stu002) {    System.out.println(stu002.getName());   }      // 获取打印缓存池中对象数量   int cacheSize = cachePool.getSize();   System.out.println(cacheSize);      // 删除对象002   cachePool.removeCacheItem("002");     // 打印缓存池数量   cacheSize = cachePool.getSize();   System.out.println(cacheSize);  } }