如何在JAVA中实现一个固定最大size的hashMap

如何在JAVA中实现一个固定最大size的hashMap

利用LinkedHashMap的removeEldestEntry方法，重载此方法使得这个map可以增长到最大size，之后每插入一条新的记录就会删除一条最老的记录。

import java.util.LinkedHashMap;
import java.util.Map;

public class MaxSizeHashMap<K, V> extends LinkedHashMap<K, V> {
    private final int maxSize;

    public MaxSizeHashMap(int maxSize) {
        this.maxSize = maxSize;
    }

    //
    //Returns true if this map should remove its eldest entry.
    //This method is invoked by put and putAll after inserting a new entry into the map.
    //It provides the implementor with the opportunity to remove the eldest entry each time a new
    //one is added. This is useful if the map represents a cache:
    //    it allows the map to reduce memory consumption by deleting stale entries.
    //
    @Override
    protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
        return size() > maxSize;
    }
}