java 本地cache的实现

基本概述
定义一个数据结构作为（定义cache）
定义存取数据结构的方法（定义对cache的操作）
定期任务维护数据结构（清理过期cache）

1. 定义接口

package com.yj.test.javaBases.testCache.ICache;

import java.util.Collection;
import java.util.Date;
import java.util.Set;

public interface Icache<K,V> {
    public V put(K key, V value);
    public V put(K key, V value, Date expiry);
    public V put(K key, V value, int TTL);
    public V get(K key);
    public V remove(K key);
    public boolean clear();
    public int size();
    public Set<K> keySet();
    public Collection<V> values();
    public boolean containsKey(K key);
    public void destory();
}

2. 实现接口

package com.yj.test.javaBases.testCache.Cache;

import java.util.ArrayList;
import java.util.Calendar;
import java.util.Collection;
import java.util.Date;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentHashMap.KeySetView;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import com.yj.test.javaBases.testCache.ICache.Icache;

public class MyCache implements Icache<String, Object> {
    private int moduleSize = 10;
    private ConcurrentHashMap<String, Long> expiryCache;
    private ConcurrentHashMap[] caches;
    private int initDelay = 1;
    private int period = 10;
    private TimeUnit 
    private ScheduledExecutorService scheduleService;
    private Runnable scheduledRemoveExpiredCaches;

    MyCache() {
        init();
    }

    MyCache(int initDelay, int period, TimeUnit unit, int moduleSize) {
        this.setInitDelay(initDelay);
        this.setModuleSize(moduleSize);
        this.setPeriod(period);
        this.setUnit(unit);
        init();
    }

    private void init() {
        expiryCache = new ConcurrentHashMap<String, Long>();
        caches = new ConcurrentHashMap[moduleSize];
        for (int i = 0; i < moduleSize; i++) {
            caches[i] = new ConcurrentHashMap<String, Object>();
        }
        scheduleService = Executors.newScheduledThreadPool(1);
        scheduledRemoveExpiredCaches = new Runnable() {
            public void run() {
                checkToRemoveExpiredCaches();
            }
        };
        scheduleService.scheduleAtFixedRate(scheduledRemoveExpiredCaches,
                this.getInitDelay(), this.getPeriod(), this.getUnit());
    }

    protected void checkToRemoveExpiredCaches() {
        Iterator iterator = expiryCache.keySet().iterator();
        while(iterator.hasNext()){
            String key = (String) iterator.next();
            Long value = expiryCache.get(key);
            if(value!=null&&value>0){
                if (new Date(value).before(new Date())){
                    getCache(key).remove(key);
                    this.expiryCache.remove(key);
                }
            }
        }

    }

    private ConcurrentHashMap<String,Object> getCache(String key) {
        int hashcode = key.hashCode();
        if(hashcode<0)
            hashcode = -hashcode;
        int index = hashcode%this.getModuleSize();
        return caches[index];
    }

    @Override
    public Object put(String key, Object value) {
        Object result = this.getCache(key).put(key, value);
        this.expiryCache.put(key, (long)-1);
        return result;
    }

    @Override
    public Object put(String key, Object value, Date expiry) {
        Object result = this.getCache(key).put(key, value);
        this.expiryCache.put(key, expiry.getTime());
        return result;
    }

    @Override
    public Object put(String key, Object value, int TTL) {
        Object result = this.getCache(key).put(key, value);
        Calendar calendar = Calendar.getInstance();
        calendar.add(Calendar.SECOND, TTL);
        this.expiryCache.put(key, calendar.getTimeInMillis());      
        return result;
    }

    @Override
    public Object get(String key) {
        checkVaild(key);
        return this.getCache(key).get(key);
    }

    private void checkVaild(String key) {
        long value = this.expiryCache.get(key);
        if(value>0){
            if((new Date(value)).before(new Date())){}
            this.expiryCache.remove(key);
            getCache(key).remove(key);
        }
    }

    @Override
    public Object remove(String key) {
        this.expiryCache.remove(key);
        Object result = this.getCache(key).remove(key);
        return result;
    }

    @Override
    public boolean clear() {
        if(expiryCache!=null){
            expiryCache.clear();
        }
        if(caches!=null){
            for(ConcurrentHashMap<String,Object> cache: caches){
                cache.clear();
            }
        }
        return true;
    }

    @Override
    public int size() {
        checkAll();
        int size = 0;
        for(ConcurrentHashMap<String,Object> cache:caches){
            size += cache.size();
        }
        return size;
    }

    private void checkAll() {
        Iterator<String> iterator = this.expiryCache.keySet().iterator();
        while(iterator.hasNext()){
            this.checkVaild(iterator.next());
        }
    }

    @Override
    public Set<String> keySet() {
        checkAll();
        return this.expiryCache.keySet();
    }

    @Override
    public Collection<Object> values() {
        checkAll();
        Collection<Object> values =new ArrayList<Object>();
        for(ConcurrentHashMap<String,Object> cache: caches){
            values.addAll(cache.values());
        }
        return values;
    }

    @Override
    public boolean containsKey(String key) {
        checkAll();     
        return this.getCache(key).contains(key);
    }

    @Override
    public void destory() {
        this.clear();
        if (this.scheduleService != null){
            this.scheduleService.shutdown();
        }
        this.scheduleService = null;
    }

    public int getModuleSize() {
        return moduleSize;
    }

    public void setModuleSize(int moduleSize) {
        this.moduleSize = moduleSize;
    }

    public int getInitDelay() {
        return initDelay;
    }

    public void setInitDelay(int initDelay) {
        this.initDelay = initDelay;
    }

    public int getPeriod() {
        return period;
    }

    public void setPeriod(int period) {
        this.period = period;
    }

    public TimeUnit getUnit() {
        return unit;
    }

    public void setUnit(TimeUnit unit) {
        this.unit = unit;
    }

}