【狂神說Java】實現多執行緒:Runnable介面
阿新 • • 發佈:2021-09-14
執行緒建立
- Thread:繼承Thread類(重點)
- Runnable:實現Runnable介面(重點,推薦)
- Callable:實現Callable介面(瞭解)
實現Runnable介面
- 定義MyRunnable類實現Runable介面
- 實現run()方法,編寫執行緒執行體
- 建立執行緒物件,呼叫start()方法啟動執行緒
推薦使用Runnable介面,因為Java是單繼承,但介面可以實現多個
執行緒開啟不一定立即執行,需要看CPU的排程
public class StartRunnable implements Runnable{ @Override public void run() { // 執行緒體 for (int i = 0; i < 200; i++) { System.out.println("Runnable介面實現多執行緒"); } } public static void main(String[] args) { // 呼叫執行緒 StartRunnable startRunnable = new StartRunnable(); // 需要用Thread物件,只有在Thread中有start方法,代理 Thread thread = new Thread(startRunnable); // 啟動 thread.start(); for (int i = 0; i < 200; i++) { System.out.println("順序執行?"); } } }
Thread類也實現了Runnable介面,這倆實際都是是完成run()方法的重寫。Runnable多了一步操作需要Thread做代理再呼叫start方法。
- 下載圖片,實現Runnable介面
public class PicThread implements Runnable{ private String url = ""; // 網路圖片地址 private String name = ""; // 儲存路徑 // 構造器,初始化地址 public PicThread(String url,String name){ this.url = url; this.name = name; } @Override public void run() { WebDownloader webDownloader = new WebDownloader(); webDownloader.downloader(url, name); System.out.println("路徑"+name); } // 啟動執行緒 public static void main(String[] args) { String url = "https://img0.bdstatic.com/static/searchdetail/img/logo-2X_2dd9a28.png"; String name = "C:\\Users\\Jie7\\IdeaProjects\\Test\\src\\baidulogo"; // 多執行緒,啟動,無序 PicThread picThread1 = new PicThread(url, name +"1.png"); PicThread picThread2 = new PicThread(url, name +"2.png"); PicThread picThread3 = new PicThread(url, name +"3.png"); // Thread 代理,傳入 Runnable物件 Thread t1 = new Thread(picThread1); Thread t2 = new Thread(picThread2); Thread t3 = new Thread(picThread3); // 呼叫 t1.start(); t2.start(); t3.start(); } } class WebDownloader { // 遠端下載 // 遠端路徑,儲存地址+名字 public void downloader(String url, String name) { try { FileUtils.copyURLToFile(new URL(url), new File(name)); } catch (IOException e) { e.printStackTrace(); System.out.println("檔案下載失敗"); } } }