java多線程之Concurrent.Utils常用類Semaphore詳解

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程式碼範例：

public class UseSemaphore {        public static void main(String[] args) {          // 線程池          ExecutorService exec = Executors.newCachedThreadPool();          // 只能5個線程同時訪問          final Semaphore semp = new Semaphore(5);          // 類比20個用戶端訪問          for (int index = 0; index < 20; index++) {              final int NO = index;              Runnable run = new Runnable() {                  public void run() {                      try {                          // 擷取許可  同時只有5個線程進入執行                        semp.acquire();                          System.out.println("Accessing: " + NO);                          //類比實際商務邏輯                        Thread.sleep((long) (Math.random() * 10000));                          // 訪問完後，釋放                          semp.release();                      } catch (InterruptedException e) {                      }                  }              };              exec.execute(run);          }                 try {            Thread.sleep(10);        } catch (InterruptedException e) {            e.printStackTrace();        }        //System.out.println(semp.getQueueLength());        // 退出線程池          exec.shutdown();      }  }  

java多線程之Concurrent.Utils常用類Semaphore詳解