Java实现缓存，类似于Redis的实现，可以缓存对象到内存中，提高访问效率。代码如下：
import java.util.ArrayList;import java.util.HashMap;import java.util.Iterator;/** * <p>Description: 管理缓存</p> * 可扩展的功能：当cache到内存溢出时必须清除掉最早期的一些缓存对象，这就要求对每个缓存对象保存创建时间 * 目前该缓存管理器仅仅支持IOS客户端访问时的登录状态管理，如果进行它用，请防止key冲突* @author yuancodenet*/ 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<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<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; } } //获取缓存对象中指定类型 的键值名称 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; } } }
测试一下：
/** * <p>Description: 缓存DTO</p> * @author yuancodenet*/ 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; } } 如何使用：public static void main(String[] args) {//Demo1Cache c1 = new Cache();c1.setKey("China");c1.setValue("中华人民共和国");Cache c2 = new Cache();c2.setKey("American");c2.setValue("美利坚合众国");CacheManager.putCache("one", c1);CacheManager.putCache("two", c2);System.out.println("缓存大小："+CacheManager.getCacheSize());System.out.println("key为one的缓存对象Value："+CacheManager.getCacheInfo("one").getValue());System.out.println("-----------------------------------");//Demo2Cache c3 = new Cache();c3.setKey("小客车品牌列表");List<String> list1 = new ArrayList<String>();list1.add("奔驰");list1.add("宝马");list1.add("奥迪");list1.add("现代");c3.setValue(list1);CacheManager.putCache("car", c3);List<String> list2 = new ArrayList<String>();Object obCar = CacheManager.getCacheInfo("car").getValue();if(obCar instanceof List){list2 = (List<String>) obCar;}for(String brand : list2){System.out.println("Key为car的品牌："+brand);}System.out.println("-----------------------------------");//Demo3Cache c4 = new Cache();c4.setKey("朗行-自动1.8T");Cache c5 = new Cache();c5.setKey("朗境-双离合2.0T");Cache c6 = new Cache();c6.setKey("夏朗-自动1.8T");Cache c7 = new Cache();c7.setKey("朗逸-双离合2.0T");Cache c8 = new Cache();c8.setKey("速腾-自动1.8T");Cache c9 = new Cache();c9.setKey("迈腾-双离合2.0T");Cache c10 = new Cache();c10.setKey("辉腾-双离合2.0T");Map<String,String> map1 = new HashMap<String,String>();map1.put("全景天窗", "是");map1.put("发动机排量", "2.0L");map1.put("排放标准", "国5");c10.setValue(map1);Cache c11 = new Cache();c11.setKey("英菲尼迪-1.8T都市精英版");CacheManager.putCache("朗行", c4);CacheManager.putCache("朗境", c5);CacheManager.putCache("朗逸", c6);CacheManager.putCache("夏朗", c7);CacheManager.putCache("速腾", c8);CacheManager.putCache("迈腾", c9);CacheManager.putCache("辉腾", c10);//得到朗系家族的车产品Object carObj2 = CacheManager.getCacheListLikekey("朗");List<String> list3 = new ArrayList<String>();if(carObj2 instanceof List){list3 = (List<String>) carObj2;}for(String product : list3){System.out.println("朗系家族："+product);}System.out.println("-----------------------------------");//得到X腾系列的车产品Object carObj3 = CacheManager.getCacheListLikekey("腾");List<String> list4 = new ArrayList<String>();if(carObj2 instanceof List){list4 = (List<String>) carObj3;}for(String product : list4){System.out.println("腾系家族："+product);}System.out.println("-----------------------------------");System.out.println("此时的缓存大小："+CacheManager.getCacheSize());}
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