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AJAXJS aims to full-stack, not only the server-side framework, but also integrates the front-end library. It's written in HTML5 + Java, a successor to the JVM platform, efficient, secure, stable, cross-platform and many other advantages, but it abandoned the traditional enterprise architecture brought about by the large and bloated, emphasizing the lightweight, and fast, very suitable for the Internet fast application.

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package com.ajaxjs.net.http;

import java.util.Arrays;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.function.Supplier;

/**
 * 图片批量下载
 * 
 * @author Frank Cheung
 *
 */
public class PicDownload {
	public CountDownLatch latch;
	private String[] arr;
	private String saveFolder;
	private Supplier newFileNameFn;

	/**
	 * 
	 * @param arr
	 * @param saveFolder
	 * @param newFileNameFn How to specify a new file name, if it is null then use
	 * old name
	 */
	public PicDownload(String[] arr, String saveFolder, Supplier newFileNameFn) {
		latch = new CountDownLatch(arr.length);
		this.arr = arr;
		this.saveFolder = saveFolder;
		this.newFileNameFn = newFileNameFn;
	}

	/**
	 * Download
	 * 
	 * @param url
	 * @param i
	 */
	public void exec(String url, int i) {
		String newFileName;

		try {
//			System.out.println(Thread.currentThread().getName() + " 开始下载");
			if (newFileNameFn == null) {
				newFileName = NetUtil.download(url, saveFolder);
			} else {
				newFileName = NetUtil.download(url, saveFolder, newFileNameFn.get());
			}

//			System.out.println(Thread.currentThread().getName() + " 下载完成");
			String[] _arr = newFileName.split("\\\\");
			String f = _arr[_arr.length - 1];
			arr[i] = f;
		} finally {
			latch.countDown();// 每个子线程中，不管是否成功，是否有异常
		}
	}

	public void start() {
		for (int i = 0; i < arr.length; i++) {
			final int j = i;
			new Thread(() -> exec(arr[j], j)).start();
		}

		try {
			latch.await(20, TimeUnit.SECONDS); // 给主线程设置一个最大等待超时时间 20秒
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}

	public static void main(String[] args) throws InterruptedException {
		String[] testArr = new String[] { "https://bbsimage.res.meizu.com/forum/2019/01/23/153122zrz85kuvubbiibbs.jpg", "http://531.yishu1000.com/201906/004/1.jpg", "http://531.yishu1000.com/201906/004/2.jpg",
				"http://531.yishu1000.com/201906/004/3.jpg" };

		new PicDownload(testArr, "c:/temp", null).start();

		System.out.println("全部完成" + Arrays.toString(testArr));
	}
}