創建線程的第三種方式——使用Callable接口
阿新 • • 發佈:2018-06-13
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Callable是類似於Runnable的接口,實現Callable的類和實現Runnable的類都是可被其他線程執行的任務。
優點:有返回值
缺點:實現繁瑣
簡單實現:
CallableAndFuture.java
/** * 簡單實現 * * @author :liuqi * @date :2018-06-13 11:10. */ public class CallableAndFuture { static class MyThread implements Callable<String> { @Override public String call() throwsException { return "Hello world"; } } public static void main(String[] args) { ExecutorService threadPool = Executors.newSingleThreadExecutor(); Future<String> future = threadPool.submit(new MyThread()); try { System.out.println(future.get()); }catch (Exception e) { } finally { threadPool.shutdown(); } } }
運行結果:
Hello world
進階:
Race.java
/** * 實現callable類 * * @author :liuqi * @date :2018-06-13 10:13. */ public class Race implements Callable<Integer> { private String name; private long time;private boolean flag = true; // 步數 private int step = 0; public Race(){ } public Race(String name,int time){ super(); this.name = name; this.time = time; } @Override public Integer call() throws Exception { while(flag){ Thread.sleep(time); step++; } return step; } public String getName() { return name; } public void setName(String name) { this.name = name; } public long getTime() { return time; } public void setTime(long time) { this.time = time; } public boolean isFlag() { return flag; } public void setFlag(boolean flag) { this.flag = flag; } public int getStep() { return step; } public void setStep(int step) { this.step = step; } }
Demo05.java
/** * 使用collable接口創建線程 * * @author :liuqi * @date :2018-06-13 10:22. */ public class Demo05 { public static void main(String[] args) throws InterruptedException,ExecutionException { // 創建兩個線程 ExecutorService ser = Executors.newFixedThreadPool(2); Race tortoise = new Race("烏龜",1000); Race rabbit = new Race("兔子",500); // 獲取future對象 Future<Integer> result1 = ser.submit(tortoise); Future<Integer> result2 = ser.submit(rabbit); // 2秒 Thread.sleep(2000); // 停止線程體循環 tortoise.setFlag(false); rabbit.setFlag(false); // 獲取值 int num1 = result1.get(); int num2 = result2.get(); System.out.println("烏龜跑了 " + num1 + "步"); System.out.println("兔子跑了 " + num2 + "步"); // 停止服務 ser.shutdownNow(); } }
運行結果:
烏龜跑了 3步
兔子跑了 5步
代碼地址:https://github.com/yuki9467/TST-javademo/tree/master/src/main/thread
Callable和Runnable有幾點不同:
1.Callable規定方法是call(),而Runnable規定方法是run();
2.Callable任務執行後可返回值,而Runnable不能返回值;
3.call()可拋出異常,而run()不能拋出異常;
4.運行Callable任務可拿到一個Future對象,Future表示異步計算的結果,通過Future對象可了解任務執行情況,可取消任務的執行,還可獲取任務執行的結果。
創建線程的第三種方式——使用Callable接口