java 两种缓存

JAVA缓存有两种: 
一、文件缓存,是指把数据存储在磁盘上，可以XML格式，也可以序列化文件DAT格式还是其它文件格式。 
二、内存缓存，也就是实现一个类中静态Map,对这个Map进行常规的增删查。

其代码如下：

目录 [隐藏] 
1 Cache类 
2 CacheManager类 
 JAVA缓存-Cache类        
public class Cache { 
private String key;//缓存ID 
private Object value;//缓存数据 
private long timeOut;//更新时间 
private boolean expired; //是否终止 
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; 
} 
} 
//测试类， 
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("删除前的大小："+CacheManager.getCacheSize()); 
// CacheManager.getCacheAllkey(); 
// CacheManager.clearAll("aaaa"); 
// System.out.println("删除后的大小："+CacheManager.getCacheSize()); 
// CacheManager.getCacheAllkey(); 
} 
}

JAVA缓存-CacheManager类        public class CacheManager { 
private static HashMap cacheMap = new HashMap(); 
//单实例构造方法 
private CacheManager() { 
super(); 
} 
//获取布尔值的缓存 
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; 
} 
} 
//设置布尔值的缓存 
public synchronized static boolean setSimpleFlag(String key,boolean flag){ 
if (flag && getSimpleFlag(key)) {//假如为真不允许被覆盖 
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; 
} 
} 
//得到缓存。同步静态方法 
private synchronized static Cache getCache(String key) { 
return (Cache) cacheMap.get(key); 
} 
//判断是否存在一个缓存 
private synchronized static boolean hasCache(String key) { 
return cacheMap.containsKey(key); 
}
//清除所有缓存 
public synchronized static void clearAll() { 
cacheMap.clear(); 
} 
//清除某一类特定缓存,通过遍历HASHMAP下的所有对象，来判断它的KEY与传入的TYPE是否匹配 
public synchronized static void clearAll(String type) { 
Iterator i = cacheMap.entrySet().iterator(); 
String key; 
ArrayList arr = new ArrayList(); 
try { 
while (i.hasNext()) { 
java.util.Map.Entry entry = (java.util.Map.Entry) i.next(); 
key = (String) entry.getKey(); 
if (key.startsWith(type)) { //如果匹配则删除掉 
arr.add(key); 
} 
} 
for (int k = 0; k < arr.size(); k++) { 
clearOnly(arr.get(k)); 
} 
} catch (Exception ex) { 
ex.printStackTrace(); 
} 
} 
//清除指定的缓存 
public synchronized static void clearOnly(String key) { 
cacheMap.remove(key); 
} 
//载入缓存 
public synchronized static void putCache(String key, Cache obj) { 
cacheMap.put(key, obj); 
} 
//获取缓存信息 
public static Cache getCacheInfo(String key) { 
if (hasCache(key)) { 
Cache cache = getCache(key); 
if (cacheExpired(cache)) { //调用判断是否终止方法 
cache.setExpired(true); 
} 
return cache; 
}else 
return null; 
} 
//载入缓存信息 
public static void putCacheInfo(String key, Cache obj, long dt,boolean expired) { 
Cache cache = new Cache(); 
cache.setKey(key); 
cache.setTimeOut(dt + System.currentTimeMillis()); //设置多久后更新缓存 
cache.setValue(obj); 
cache.setExpired(expired); //缓存默认载入时，终止状态为FALSE 
cacheMap.put(key, cache); 
} 
//重写载入缓存信息方法 
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); 
} 
//判断缓存是否终止 
public static boolean cacheExpired(Cache cache) { 
if (null == cache) { //传入的缓存不存在 
return false; 
} 
long nowDt = System.currentTimeMillis(); //系统当前的毫秒数 
long cacheDt = cache.getTimeOut(); //缓存内的过期毫秒数 
if (cacheDt <= 0||cacheDt>nowDt) { //过期时间小于等于零时,或者过期时间大于当前时间时，则为FALSE 
return false; 
} else { //大于过期时间 即过期 
return true; 
} 
} 
//获取缓存中的大小 
public static int getCacheSize() { 
return cacheMap.size(); 
} 
//获取指定的类型的大小 
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) { //如果匹配则删除掉 
k++; 
} 
} 
} catch (Exception ex) { 
ex.printStackTrace(); 
} 
return k; 
} 
//获取缓存对象中的所有键值名称 
public static ArrayList 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; 
} 
} 
//获取缓存对象中指定类型 的键值名称 
public static ArrayList 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; 
} 
} 
}