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基于Java实现缓存Cache的深入分析
来源: 互联网 发布时间:2014-10-26
本文导语: 原理是使用LinkedHashMap来实现,当缓存超过大小时,将会删除最老的一个元组。实现代码如下所示 代码如下:import java.util.LinkedHashMap;import java.util.Map;public class LRUCache { public static class CachedData { private Object data = null; private long...
原理是使用LinkedHashMap来实现,当缓存超过大小时,将会删除最老的一个元组。
实现代码如下所示
import java.util.LinkedHashMap;
import java.util.Map;
public class LRUCache {
public static class CachedData {
private Object data = null;
private long time = 0;
private boolean refreshing = false;
public CachedData(Object data) {
this.data = data;
this.time = System.currentTimeMillis();
}
public Object getData() {
return data;
}
public long getTime() {
return time;
}
public void setTime(long time) {
this.time = time;
}
public boolean getRefreshing() {
return refreshing;
}
public void setRefreshing(boolean b) {
this.refreshing = b;
}
}
protected static class CacheMap extends LinkedHashMap {
protected int maxsize = 0;
public CacheMap(int maxsize) {
super(maxsize * 4 / 3 + 1, 0.75f, true);
this.maxsize = maxsize;
}
protected boolean removeEldestEntry(Map.Entry eldest) {
return size() > this.maxsize;
}
}
protected CacheMap map = null;
public LRUCache(int size) {
this.map = new CacheMap(size);
}
public synchronized void set(Object key, Object value) {
map.remove(key);
map.put(key, new CachedData(value));
}
public synchronized void remove(Object key) {
map.remove(key);
}
public synchronized CachedData get(Object key) {
CachedData value = (CachedData) map.get(key);
if (value == null) {
return null;
}
map.remove(key);
map.put(key, value);
return value;
}
public int usage() {
return map.size();
}
public int capacity() {
return map.maxsize;
}
public void clear() {
map.clear();
}
}
实现代码如下所示
代码如下:
import java.util.LinkedHashMap;
import java.util.Map;
public class LRUCache {
public static class CachedData {
private Object data = null;
private long time = 0;
private boolean refreshing = false;
public CachedData(Object data) {
this.data = data;
this.time = System.currentTimeMillis();
}
public Object getData() {
return data;
}
public long getTime() {
return time;
}
public void setTime(long time) {
this.time = time;
}
public boolean getRefreshing() {
return refreshing;
}
public void setRefreshing(boolean b) {
this.refreshing = b;
}
}
protected static class CacheMap extends LinkedHashMap {
protected int maxsize = 0;
public CacheMap(int maxsize) {
super(maxsize * 4 / 3 + 1, 0.75f, true);
this.maxsize = maxsize;
}
protected boolean removeEldestEntry(Map.Entry eldest) {
return size() > this.maxsize;
}
}
protected CacheMap map = null;
public LRUCache(int size) {
this.map = new CacheMap(size);
}
public synchronized void set(Object key, Object value) {
map.remove(key);
map.put(key, new CachedData(value));
}
public synchronized void remove(Object key) {
map.remove(key);
}
public synchronized CachedData get(Object key) {
CachedData value = (CachedData) map.get(key);
if (value == null) {
return null;
}
map.remove(key);
map.put(key, value);
return value;
}
public int usage() {
return map.size();
}
public int capacity() {
return map.maxsize;
}
public void clear() {
map.clear();
}
}