用callable介面和runnable介面實現多執行緒同步下載圖片
阿新 • • 發佈：2021-11-27
//執行緒建立方式三：實現callable介面
/*
callable的好處
1、可以定義返回值
2、可以丟擲異常
*/
public class TestCallable implements Callable<Boolean> {
private String url;//網路圖片地址
private String name;//儲存的檔名
public TestCallable(String url,String name){
this.url = url;
this.name = name;
}
//下載圖片執行緒的執行體
@Override
public Boolean call() {
WebDownloader webDownloader = new WebDownloader();
webDownloader.downloader(url,name);
System.out.println("下載的檔名為："+name);
return true;
}
public static void main(String[] args) throws ExecutionException, InterruptedException {
TestCallable t1 = new TestCallable("https://www.wahaotu.com/uploads/allimg/201904/1555074510295049.jpg\n","1.jpg");
TestCallable t2 = new TestCallable("https://www.wahaotu.com/uploads/allimg/201904/1555074510295049.jpg\n","2.jpg");
TestCallable t3 = new TestCallable("https://www.wahaotu.com/uploads/allimg/201904/1555074510295049.jpg\n","3.jpg");
//建立執行服務：
ExecutorService ser = Executors.newFixedThreadPool(3);
//提交執行
Future<Boolean> r1 = ser.submit(t1);
Future<Boolean> r2 = ser.submit(t2);
Future<Boolean> r3 = ser.submit(t3);
//獲取結果
boolean rs1 = r1.get();
boolean rs2 = r2.get();
boolean rs3 = r3.get();
System.out.println(rs1);
System.out.println(rs2);
System.out.println(rs3);
//關閉服務
ser.shutdownNow();
}
}
//下載器
class WebDownloader{
//下載方法 URL資源定位器
public void downloader(String url,String name){
try {
FileUtils.copyURLToFile(new URL(url),new File(name));
} catch (IOException e) {
e.printStackTrace();
System.out.println("IO異常，downloader方法出現問題");
}
}
}
==============================================================================
實現runnable介面,實現多執行緒同步下載圖片
public class TestThread2 implements Runnable{
private String url;//網路圖片地址
private String name;//儲存的檔名
public TestThread2(String url,String name){
this.url = url;
this.name = name;
}
//下載圖片執行緒的執行體
@Override
public void run() {
WebDownloader webDownloader = new WebDownloader();
webDownloader.downloader(url,name);
System.out.println("下載的檔名為："+name);
}
public static void main(String[] args) {
TestThread2 t1 = new TestThread2("https://www.wahaotu.com/uploads/allimg/201904/1555074510295049.jpg\n","1.jpg");
TestThread2 t2 = new TestThread2("https://www.wahaotu.com/uploads/allimg/201904/1555074510295049.jpg\n","2.jpg");
TestThread2 t3 = new TestThread2("https://www.wahaotu.com/uploads/allimg/201904/1555074510295049.jpg\n","3.jpg");
//呼叫start()方法並不是按順序執行，每次執行的順序不一樣，呼叫的順序由CPU決定
new Thread(t1).start();
new Thread(t2).start();
new Thread(t3).start();
}
}
//下載器
class WebDownloader{
//下載方法 URL資源定位器
public void downloader(String url,String name){
try {
FileUtils.copyURLToFile(new URL(url),new File(name));
} catch (IOException e) {
e.printStackTrace();
System.out.println("IO異常，downloader方法出現問題");
}
}
}