net.jkcode.jkmvc.common.LazyAllocatedMap Maven / Gradle / Ivy

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package net.jkcode.jkmvc.common;

import java.io.Serializable;
import java.util.*;

/**
 * 延迟申请内存的map
 *    线程不安全, 尽量在单线程中使用
 *
 * @deprecated 其实我搞错了, HashMap的table数组数组也是延迟创建, 只要没有put(), table即为null
 *             真正的优化在于 FixedKeyMap
 * @author shijianhang<[email protected]>
 * @date 2019-03-31 9:43 PM
 */
public class LazyAllocatedMap extends AbstractMap implements Serializable {

    /**
     * 被代理的map
     */
    protected Map map = Collections.EMPTY_MAP;

    /**
     * 获得可添加元素的map
     * @return
     */
    protected Map getPutableMap(){
        if(map == Collections.EMPTY_MAP)
            map = new HashMap();
        return map;
    }

    @Override
    public V get(final Object key) {
        return map.get(key);
    }

    @Override
    public boolean isEmpty() {
        return map.isEmpty();
    }

    @Override
    public boolean containsValue(final Object value) {
        return map.containsValue(value);
    }

    @Override
    public boolean containsKey(final Object key) {
        return map.containsKey(key);
    }

    @Override
    public V put(final K key, final V value) {
        return getPutableMap().put(key, value);
    }

    @Override
    public void putAll(final Map m) {
        getPutableMap().putAll(m);
    }

    @Override
    public V remove(final Object key) {
        if(map == Collections.EMPTY_MAP)
            return null;

        return map.remove(key);
    }

    @Override
    public void clear() {
        if(map == Collections.EMPTY_MAP)
            return;

        map.clear();
    }

    @Override
    public Set keySet() {
        return map.keySet();
    }

    @Override
    public Collection values() {
        return map.values();
    }

    @Override
    public int size() {
        return map.size();
    }

    @Override
    public Set> entrySet() {
        return map.entrySet();
    }
}