Java中的BlockingQueue take()方法（附例子）

BlockingQueue 接口中的 take() 方法用于检索和删除此队列的头部。如果队列为空，它将等待直到有元素可用。如果在线程中使用BlockingQueue，则此方法更有效率。因此，最初调用take()的线程会进入睡眠状态，直到有元素可用，其它线程则可以做它们需要做的事情。

语法:

public E take() throws InterruptedException

返回值: 如果队列为空，则此方法返回此BlockingQueue的头部值，并等待直到有元素可用。

异常: 此方法会抛出以下异常:

• InterruptedException – 当在等待一个元素变得可用时，如果队列为空，就会发生中断。

注意: : Java中的 BlockingQueue take() 方法已从 Queue 类继承了下来。

下面的程序演示了BlockingQueue接口的take()方法：

程序1:

代码如下：

// Java Program Demonstrate take()
// method of BlockingQueue
 
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.BlockingQueue;
public class GFG {
 
    public static void main(String[] args)
        throws InterruptedException
    {
        // define capacity of BlockingQueue
        int capacityOfQueue = 4;
 
        // create object of BlockingQueue
        BlockingQueue<String> BQ
            = new LinkedBlockingQueue<String>(capacityOfQueue);
 
        // Add element to BlockingQueue
        BQ.add("Ravi");
        BQ.add("Suraj");
        BQ.add("Harsh");
        BQ.add("Sayan");
 
        // print elements of queue
        System.out.println("Items in Queue are " + BQ);
 
        // remove two elements from queue from head
        // Applying take() method on queue to remove element
        String removedItem1 = BQ.take();
 
        // print removedItem and queue
        System.out.println("Removed Item from head is "
                           + removedItem1);
 
        // print elements of queue after removing first item
        System.out.println("Remaining Items in Queue are "
                           + BQ);
 
        // Applying take() method on queue to remove another element
        String removedItem2 = BQ.take();
 
        // print removedItem and queue
        System.out.println("Removed Item from head is "
                           + removedItem2);
 
        // print elements of queue after removing first item
        System.out.println("Remaining Items in Queue are "
                           + BQ);
    }
}

输出:

Items in Queue are [Ravi, Suraj, Harsh, Sayan]
Removed Item from head is Ravi
Remaining Items in Queue are [Suraj, Harsh, Sayan]
Removed Item from head is Suraj
Remaining Items in Queue are [Harsh, Sayan]

程序2:

// Java程序演示BlockingQueue的take()方法
 
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.BlockingQueue;
 
public class GFG {
 
    public void takeDemo() throws InterruptedException
    {
        // 定义BlockingQueue的容量
        int capacityOfQueue = 5;
 
        // 创建BlockingQueue对象
        BlockingQueue<Employee> BQ
            = new LinkedBlockingQueue<Employee>(capacityOfQueue);
 
        // 添加元素到BlockingQueue
        Employee emp1 = new Employee("Ravi", "测试员", "39000");
        Employee emp2 = new Employee("Sanjeet", "经理", "98000");
 
        // 将员工对象添加到BQ
        BQ.add(emp1);
        BQ.add(emp2);
 
        // 从队列中删除元素，
        // 并一遍又一遍地按此过程继续，
        // 直到队列变为空为止
        while (BQ.size() != 0) {
 
            // 使用take()方法从BlockingQueue中删除Employee项
            Employee removedEmp = BQ.take();
 
            // 打印已删除的项
            System.out.println("已删除的项是：");
            System.out.println("员工姓名 - "
                               + removedEmp.name);
            System.out.println("员工职位 - "
                               + removedEmp.position);
            System.out.println("员工工资 - "
                               + removedEmp.salary);
 
            // 查找BQ的大小
            int size = BQ.size();
 
            // 打印剩余容量值
            System.out.println("\n列表大小：" + size + "\n");
        }
    }
 
    // 使用名称、职位和工资作为属性创建一个Employee对象
    public class Employee {
 
        public String name;
        public String position;
        public String salary;
 
        Employee(String name, String position, String salary)
        {
            this.name = name;
            this.position = position;
            this.salary = salary;
        }
 
        @Override
        public String toString()
        {
            return "Employee [name=" + name + ", position="
                + position + ", salary=" + salary + "]";
        }
    }
 
    // 主方法
    public static void main(String[] args)
    {
        GFG gfg = new GFG();
        try {
            gfg.takeDemo();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}

输出：

已删除的项是：
员工姓名 - Ravi
员工职位 - 测试员
员工工资 - 39000

列表大小：1

已删除的项是：
员工姓名 - Sanjeet
员工职位 - 经理
员工工资 - 98000

列表大小：0