Java中的 ArrayBlockingQueue contains() 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。

如果队列包含作为参数传递的对象 o，则contains(Object o)方法返回 true。我们可以说，当且仅当此队列包含至少一个元素 e 等于作为参数 ieoequals(e) 传递的对象 o 时，该方法才返回 true。
句法：

public boolean contains(Object o)

范围：
o - 检查队列是否包含指定对象的对象。
返回值：
如果此队列包含对象，则为 true

下面的程序说明了包含 ArrayBlockingQueue 的方法。
示例 1

// Java Program Demonstrate contains(Object o)
// 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);
        queue.add(45);
        queue.add(12);
  
        // check whether queue contains 23
        boolean response1 = queue.contains(23);
  
        // print after applying contains method with 23 as parameter
        System.out.println("queue contains 23 : " + response1);
  
        // check whether queue contains 99
        boolean response2 = queue.contains(99);
  
        // print after applying contains method with 99 as parameter
        System.out.println("queue contains 99 : " + response2);
    }
}

输出：

queue contains 23 : true
queue contains 99 : false

示例 2

// Java Program Demonstrate contains(Object o)
// method of ArrayBlockingQueue.
import java.util.concurrent.ArrayBlockingQueue;
  
public class GFG {
  
    // create a User Object with name and age as 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.containsMethodExample();
    }
  
    // Method to give example of contains function
    public void containsMethodExample()
    {
  
        // define capacity of ArrayBlockingQueue
        int capacity = 5;
  
        // create object of ArrayBlockingQueue
        ArrayBlockingQueue queue
            = new ArrayBlockingQueue(capacity);
  
        User user1 = new User("Aman", "24");
        User user2 = new User("Amar", "23");
        User user3 = new User("Sanjeet", "25");
        User user4 = new User("Suvo", "26");
  
        // Add Objects to ArrayBlockingQueue
        queue.add(user1);
        queue.add(user2);
        queue.add(user3);
        queue.add(user4);
  
        User user5 = new User("Ravi", "22");
        // check whether queue contains User1
        boolean response1 = queue.contains(user1);
  
        // print after applying contains method with user1 as parameter
        System.out.println("queue contains User having name "
                           + user1.name + " : " + response1);
  
        // check whether queue contains User5
        boolean response2 = queue.contains(user5);
  
        // print after applying contains method with user1 as parameter
        System.out.println("queue contains User having name "
                           + user5.name + " : " + response2);
    }
}

输出：

queue contains User having name Aman : true
queue contains User having name Ravi : false

参考：
https://docs.oracle.com/javase/7/docs/api/java Java Java)