程序清单 14-11 使用显式条件变量的有界缓存

Author: zhangquanli

src/main/java/chapter_14/code_11/ConditionBoundedBuffer.java

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+package chapter_14.code_11;
+
+import net.jcip.annotations.GuardedBy;
+import net.jcip.annotations.ThreadSafe;
+
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * 程序清单 14-11 使用显式条件变量的有界缓存
+ */
+@ThreadSafe
+public class ConditionBoundedBuffer<T> {
+    protected final Lock lock = new ReentrantLock();
+    // 条件谓词：notFull (count < items.length)
+    private final Condition notFull = lock.newCondition();
+    // 条件谓词：notEmpty (count > 0)
+    private final Condition notEmpty = lock.newCondition();
+    private static final int BUFFER_SIZE = 100;
+    @GuardedBy("lock")
+    private final T[] items = (T[]) new Object[BUFFER_SIZE];
+    @GuardedBy("lock")
+    private int tail, head, count;
+
+    // 阻塞并直到：notFull
+    public void put(T x) throws InterruptedException {
+        lock.lock();
+        try {
+            while (count == items.length) {
+                notFull.await();
+            }
+            items[tail] = x;
+            if (++tail == items.length) {
+                tail = 0;
+            }
+            ++count;
+            notEmpty.signal();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    // 阻塞并直到：notEmpty
+    public T take() throws InterruptedException {
+        lock.lock();
+        try {
+            while (count == 0) {
+                notEmpty.await();
+            }
+            T x = items[head];
+            items[head] = null;
+            if (++head == items.length) {
+                head = 0;
+            }
+            --count;
+            notFull.signal();
+            return x;
+        } finally {
+            lock.unlock();
+        }
+    }
+}