package com.basic.security.utils;

import java.util.List;
import java.util.Vector;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class ConcurrentList {

    public final Lock lock = new ReentrantLock();

    public long setTime = 0;
    public List list = new Vector();

    public boolean isEmpty() {
        try {
            lock.lock();
            if (list.size() > 0) {
                return false;
            } else {
                return true;
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
        return true;
    }

    public Object getFirst() {
        try {
            lock.lock();
            if (list.size() > 0) {
                return list.get(0);
            } else {
                return null;
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
        return null;
    }

    public void setFirst(Object object) {
        try {
            lock.lock();
            if (list.size() == 0) {
                list.add(object);
                setTime = System.currentTimeMillis();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public Object getFirst(long timeout) {
        try {
            lock.lock();
            if (list.size() > 0) {
                if (System.currentTimeMillis() - setTime < timeout) {
                    return list.get(0);
                }
            } else {
                return null;
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
        return null;
    }

    public void removeFirst() {
        try {
            lock.lock();
            if (list.size() > 0) {
                list.remove(0);
                setTime = System.currentTimeMillis();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
}