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

/**
 * 先进先出缓存哈希表
 * @param <K> key，泛型
 * @param <V> value，泛型
 */
public class FIFOCache<K,V> extends LinkedHashMap<K,V> {

    private final int cacheSize;

    public FIFOCache(int cacheSize){
        this.cacheSize = cacheSize;
    }

    /***
     * 当Entry个数超过cacheSize时，删除最老的Entry
     */
    @Override
    protected boolean removeEldestEntry(Map.Entry<K,V> eldest) {
        return size() > cacheSize;
    }
}

/***
* 判断字符串是否为数字(包括小数)
*/
public static boolean isNumber(String str){
    String reg = "^[0-9]+(.[0-9]+)?$";
    return str.matches(reg);
}