JAVA緩衝的實現(轉載)__java

package com.simpleton.cache;  /**   * <p>Title: </p>   *   * <p>Description: 緩衝DTO</p>   *   * <p>Copyright: Copyright (c) 2008</p>   *   * <p>Company: </p>   *   * @author Deepblue  2008-11-11   * @version 1.0   */   public class Cache {           private String key;//緩衝ID           private Object value;//快取資料           private long timeOut;//更新時間           private boolean expired; //是否終止           public Cache() {                   super();           }              public Cache(String key, Object value, long timeOut, boolean expired) {                   this.key = key;                   this.value = value;                   this.timeOut = timeOut;                   this.expired = expired;           }              public String getKey() {                   return key;           }              public long getTimeOut() {                   return timeOut;           }              public Object getValue() {                   return value;           }              public void setKey(String string) {                   key = string;           }              public void setTimeOut(long l) {                   timeOut = l;           }              public void setValue(Object object) {                   value = object;           }              public boolean isExpired() {                   return expired;           }              public void setExpired(boolean b) {                   expired = b;           }   }   

package com.simpleton.cache;  import java.util.*;    /**   * <p>Title: </p>   *   * <p>Description: 管理緩衝</p>   * Deep blue 2008-11-28 think   * 可擴充的功能：當chche到記憶體溢出時必須清除掉最早期的一些緩衝對象，這就要求對每個緩衝對象儲存建立時間   * <p>Copyright: Copyright (c) 2008</p>   *   * <p>Company: </p>   *   * @author Deepblue  2008-11-11   * @version 1.0   */   public class CacheManager {       private static HashMap cacheMap = new HashMap();          //單一實例構造方法       private CacheManager() {           super();       }       //擷取布爾值的緩衝       public static boolean getSimpleFlag(String key){           try{               return (Boolean) cacheMap.get(key);           }catch(NullPointerException e){               return false;           }       }       public static long getServerStartdt(String key){           try {               return (Long)cacheMap.get(key);           } catch (Exception ex) {               return 0;           }       }       //設定布爾值的緩衝       public synchronized static boolean setSimpleFlag(String key,boolean flag){           if (flag && getSimpleFlag(key)) {//假如為真不允許被覆蓋               return false;           }else{               cacheMap.put(key, flag);               return true;           }       }       public synchronized static boolean setSimpleFlag(String key,long serverbegrundt){           if (cacheMap.get(key) == null) {               cacheMap.put(key,serverbegrundt);               return true;           }else{               return false;           }       }             //得到緩衝。同步靜態方法       private synchronized static Cache getCache(String key) {           return (Cache) cacheMap.get(key);       }          //判斷是否存在一個緩衝       private synchronized static boolean hasCache(String key) {           return cacheMap.containsKey(key);       }          //清除所有緩衝       public synchronized static void clearAll() {           cacheMap.clear();       }          //清除某一類特定緩衝,通過遍曆HASHMAP下的所有對象，來判斷它的KEY與傳入的TYPE是否匹配       public synchronized static void clearAll(String type) {           Iterator i = cacheMap.entrySet().iterator();           String key;           ArrayList<String> arr = new ArrayList<String>();           try {               while (i.hasNext()) {                   java.util.Map.Entry entry = (java.util.Map.Entry) i.next();                   key = (String) entry.getKey();                   if (key.startsWith(type)) { //如果匹配則刪除掉                       arr.add(key);                   }               }               for (int k = 0; k < arr.size(); k++) {                   clearOnly(arr.get(k));               }           } catch (Exception ex) {               ex.printStackTrace();           }       }          //清除指定的緩衝       public synchronized static void clearOnly(String key) {           cacheMap.remove(key);       }          //載入緩衝       public synchronized static void putCache(String key, Cache obj) {           cacheMap.put(key, obj);       }          //擷取緩衝資訊       public static Cache getCacheInfo(String key) {              if (hasCache(key)) {               Cache cache = getCache(key);               if (cacheExpired(cache)) { //調用判斷是否終止方法                   cache.setExpired(true);               }               return cache;           }else               return null;       }          //載入緩衝資訊       public static void putCacheInfo(String key, Cache obj, long dt,boolean expired) {           Cache cache = new Cache();           cache.setKey(key);           cache.setTimeOut(dt + System.currentTimeMillis()); //設定多久後更新緩衝           cache.setValue(obj);           cache.setExpired(expired); //緩衝預設載入時，終止狀態為FALSE           cacheMap.put(key, cache);       }       //重寫載入緩衝資訊方法       public static void putCacheInfo(String key,Cache obj,long dt){           Cache cache = new Cache();           cache.setKey(key);           cache.setTimeOut(dt+System.currentTimeMillis());           cache.setValue(obj);           cache.setExpired(false);           cacheMap.put(key,cache);       }          //判斷緩衝是否終止       public static boolean cacheExpired(Cache cache) {           if (null == cache) { //傳入的緩衝不存在               return false;           }           long nowDt = System.currentTimeMillis(); //系統當前的毫秒數           long cacheDt = cache.getTimeOut(); //緩衝內的到期毫秒數           if (cacheDt <= 0||cacheDt>nowDt) { //到期時間小於等於零時,或者到期時間大於目前時間時，則為FALSE               return false;           } else { //大於到期時間 即到期               return true;           }       }          //擷取緩衝中的大小       public static int getCacheSize() {           return cacheMap.size();       }          //擷取指定的類型的大小       public static int getCacheSize(String type) {           int k = 0;           Iterator i = cacheMap.entrySet().iterator();           String key;           try {               while (i.hasNext()) {                   java.util.Map.Entry entry = (java.util.Map.Entry) i.next();                   key = (String) entry.getKey();                   if (key.indexOf(type) != -1) { //如果匹配則刪除掉                       k++;                   }               }           } catch (Exception ex) {               ex.printStackTrace();           }              return k;       }          //擷取緩衝對象中的所有索引值名稱       public static ArrayList<String> getCacheAllkey() {           ArrayList a = new ArrayList();           try {               Iterator i = cacheMap.entrySet().iterator();               while (i.hasNext()) {                   java.util.Map.Entry entry = (java.util.Map.Entry) i.next();                   a.add((String) entry.getKey());               }           } catch (Exception ex) {} finally {               return a;           }       }          //擷取緩衝對象中指定類型 的索引值名稱       public static ArrayList<String> getCacheListkey(String type) {           ArrayList a = new ArrayList();           String key;           try {               Iterator i = cacheMap.entrySet().iterator();               while (i.hasNext()) {                   java.util.Map.Entry entry = (java.util.Map.Entry) i.next();                   key = (String) entry.getKey();                   if (key.indexOf(type) != -1) {                       a.add(key);                   }               }           } catch (Exception ex) {} finally {               return a;           }       }      }      //測試類別，   class Test {       public static void main(String[] args) {           System.out.println(CacheManager.getSimpleFlag("alksd"));   //        CacheManager.putCache("abc", new Cache());   //        CacheManager.putCache("def", new Cache());   //        CacheManager.putCache("ccc", new Cache());   //        CacheManager.clearOnly("");   //        Cache c = new Cache();   //        for (int i = 0; i < 10; i++) {   //            CacheManager.putCache("" + i, c);   //        }   //        CacheManager.putCache("aaaaaaaa", c);   //        CacheManager.putCache("abchcy;alskd", c);   //        CacheManager.putCache("cccccccc", c);   //        CacheManager.putCache("abcoqiwhcy", c);   //        System.out.println("刪除前的大小："+CacheManager.getCacheSize());   //        CacheManager.getCacheAllkey();   //        CacheManager.clearAll("aaaa");   //        System.out.println("刪除後的大小："+CacheManager.getCacheSize());   //        CacheManager.getCacheAllkey();       }   }