Java中的 ArrayBlockingQueue remainingCapacity() 方法

ArrayBlockingQueue是有界的阻塞队列，它在内部存储由数组支持的元素。

• ArrayBlockingQueue类是Java集合框架的成员。
• 有界意味着它将具有固定大小，您不能存储数量超过队列容量的元素。
• 队列还遵循 FIFO（先进先出）规则来存储和删除队列中的元素。
• 如果你试图将一个元素放入一个满队列或从一个空队列中取出一个元素，那么队列会阻止你。

remainingCapacity()方法返回可以添加到队列而不阻塞的更多元素的数量。这始终等于此队列的初始容量与此队列的当前大小之间的差。

句法：

public int remainingCapacity()

参数：该方法不带任何参数。

返回值：该方法返回队列的剩余容量。

下面的程序说明了 ArrayBlockingQueue 的 remainingCapacity() 方法：
方案一：

// Program to demonstrate remainingCapacity() method
// of ArrayBlockingQueue
  
import java.util.concurrent.ArrayBlockingQueue;
  
public class GFG {
  
    public static void main(String[] args)
    {
        // Define capacity of ArrayBlockingQueue
        int capacity = 5;
  
        // Create object of ArrayBlockingQueue
        ArrayBlockingQueue queue = new 
            ArrayBlockingQueue(capacity);
  
        // Add elements to ArrayBlockingQueue
        queue.add(23);
        queue.add(32);
  
        // Print queue after adding numbers
        System.out.println("Queue :" + queue);
        // Check remaining capacity
        int remainingCapacity = queue.remainingCapacity();
        System.out.println("Remaining Capacity:" + 
                                       remainingCapacity);
  
        // Add elements to ArrayBlockingQueue
        queue.add(54);
        queue.add(78);
  
        // Print queue after adding numbers
        System.out.println("Queue :" + queue);
        // Check remaining capacity
        System.out.println("Remaining Capacity:" + 
                               queue.remainingCapacity());
    }
}

输出：

Queue :[23, 32]
Remaining Capacity:3
Queue :[23, 32, 54, 78]
Remaining Capacity:1

方案二：

// Program to demonstrate remainingCapacity() method
// of ArrayBlockingQueue
  
import java.util.concurrent.ArrayBlockingQueue;
  
public class GFG {
    // Create a User Object with name and age as an attribute
    public class User {
  
        public String name;
        public String age;
        User(String name, String age)
        {
            this.name = name;
            this.age = age;
        }
    }
  
    // Main Method
    public static void main(String[] args)
    {
        GFG gfg = new GFG();
        gfg.RemainingCapacityExample();
    }
    // Method to give example of contains function
    public void RemainingCapacityExample()
    {
  
        // Define capacity of ArrayBlockingQueue
        int capacity = 5;
  
        // Create object of ArrayBlockingQueue
        ArrayBlockingQueue queue = new 
                  ArrayBlockingQueue(capacity);
  
        // Create user objects
        User user1 = new User("Aman", "24");
        User user2 = new User("Amar", "23");
        User user3 = new User("Sanjeet", "25");
  
        // Add Objects to ArrayBlockingQueue
        queue.offer(user1);
        queue.offer(user2);
        queue.offer(user3);
  
        // Check remaining capacity
        int remainingCapacity = queue.remainingCapacity();
        System.out.println("Remaining Capacity:" + 
                                       remainingCapacity);
  
        User user4 = new User("Suvo", "26");
        User user5 = new User("Ravi", "22");
          
        // Adding more objects
        queue.offer(user2);
        queue.offer(user3);
  
        // Check remaining capacity
        remainingCapacity = queue.remainingCapacity();
        System.out.println("Remaining Capacity:" + 
                                     remainingCapacity);
    }
}

输出：

Remaining Capacity:2
Remaining Capacity:0

参考： https: Java/util/concurrent/ArrayBlockingQueue.html#remainingCapacity()