1.1.4 方法acquireUninterruptibly()的使用

方法acquireUninterruptibly()的作用是使等待進入acquire()方法的線程，不允許被中斷。

先來看一個能中斷的實驗。

創建項目Semaphore_acquireUninterruptibly_1，類Service.java代碼如下：

---

        package service;
        import java.util.concurrent.Semaphore;
        public class Service {
            private Semaphore semaphore = new Semaphore(1);
            public void testMethod() {
                try {
                    semaphore.acquire();
                    System.out.println(Thread.currentThread().getName()
                              + " begin timer=" + System.currentTimeMillis());
                    for (int i = 0; i < Integer.MAX_VALUE / 50; i++) {
                        String newString = new String();
                        Math.random();
                    }
                    System.out.println(Thread.currentThread().getName()
                              + "    end timer=" + System.currentTimeMillis());
                    semaphore.release();
                } catch (InterruptedException e) {
                    System.out.println("線程" + Thread.currentThread().getName()
                              + "進入了catch");
                    e.printStackTrace();
                }
            }
        }

---

線程類代碼如圖1-9所示。

運行類Run.java代碼如下：

---

        package test;
        import service.Service;
        import extthread.ThreadA;
        import extthread.ThreadB;
        public class Run {
            public static void main(String[] args) throws InterruptedException {
              Service service = new Service();
              ThreadA a = new ThreadA(service);
              a.setName("A");
              a.start();
              ThreadB b = new ThreadB(service);
              b.setName("B");
              b.start();
              Thread.sleep(1000);
              b.interrupt();
              System.out.println("main中斷了a");
          }
      }

---

程序運行的效果如圖1-10所示。

線程B成功被中斷。

那么不能被中斷是什么效果呢？

創建項目Semaphore_acquireUninterruptibly_2，將Semaphore_acquireUninterruptibly_1項目中的所有源代碼復制到Semaphore_acquireUninterruptibly_2中，更改Service.java文件代碼如下：

---

        package service;
        import java.util.concurrent.Semaphore;
        public class Service {
            private Semaphore semaphore = new Semaphore(1);
            public void testMethod() {
                semaphore.acquireUninterruptibly();
                System.out.println(Thread.currentThread().getName() + " begin timer="
                        + System.currentTimeMillis());
                for (int i = 0; i < Integer.MAX_VALUE / 50; i++) {
                    String newString = new String();
                    Math.random();
                }
                System.out.println(Thread.currentThread().getName() + "    end timer="
                        + System.currentTimeMillis());
                semaphore.release();
            }
        }

---

程序運行后的效果如圖1-11所示。

acquireUninterruptibly()方法還有重載的寫法acquire-Uninterruptibly(int permits)，此方法的作用是在等待許可的情況下不允許中斷，如果成功獲得鎖，則取得指定的permits許可個數。