Java中的LinkedBlockingQueue size() 方法

LinkedBlockingQueue 的size()方法返回 LinkedBlockingQueue 包含的元素数量。当队列为空队列时，size() 返回 0，当队列已满时，size() 返回队列的容量。
句法：

public int size()

返回值：此方法返回该时刻 LinkedBlockingQueue 中的元素数。返回类型是 int。
下面的程序说明了 LinkedBlockingQueue 类的 size() 方法：
程序 1：对 LinkedBlockingQueue 执行添加和删除操作，每次操作后使用 size() 打印队列大小

Java

// Java Program Demonstrate size()
// method of LinkedBlockingQueue
 
import java.util.concurrent.LinkedBlockingQueue;
 
public class GFG {
 
    public static void main(String[] args)
        throws InterruptedException
    {
        // define capacity of LinkedBlockingQueue
        int capacityOfQueue = 4;
 
        // create object of LinkedBlockingQueue
        LinkedBlockingQueue linkedQueue
            = new LinkedBlockingQueue(capacityOfQueue);
 
        // Add element using put() method
        linkedQueue.put("Karan");
        linkedQueue.put("Suraj");
 
        // get size of queue using size() method
        int size = linkedQueue.size();
 
        // print elements of queue and size of queue
        System.out.println("Items in Queue are " + linkedQueue);
        System.out.println("Size of Queue is " + size);
 
        // add more elements
        linkedQueue.put("Harsh");
        linkedQueue.put("Rahul");
 
        // get size of queue using size() method
        size = linkedQueue.size();
 
        // print elements of queue and size of queue
        System.out.println("Items in Queue are " + linkedQueue);
        System.out.println("Size of Queue is " + size);
 
        // try to remove element from Queue
        boolean try1 = linkedQueue.remove("Karan");
        System.out.println("String name Karan is removed :"
                           + try1);
 
        // get size of queue using size() method
        size = linkedQueue.size();
 
        // print elements of queue and size of queue
        System.out.println("Items in Queue are " + linkedQueue);
        System.out.println("Size of Queue is " + size);
    }
}

输出：

Items in Queue are [Karan, Suraj]
Size of Queue is 2

Items in Queue are [Karan, Suraj, Harsh, Rahul]
Size of Queue is 4

String name Karan is removed :true
Items in Queue are [Suraj, Harsh, Rahul]
Size of Queue is 3

程序 2：对包含 Employee 对象的 LinkedBlockingQueue 执行添加和删除操作，每次操作后使用 size() 打印队列大小

Java

// Java Program Demonstrate size()
// method of LinkedBlockingQueue
 
import java.util.Iterator;
import java.util.concurrent.LinkedBlockingQueue;
 
public class GFG {
 
    public void sizeDemo() throws InterruptedException
    {
        // define capacity of LinkedBlockingQueue
        int capacityOfQueue = 5;
 
        // create object of LinkedBlockingQueue
        LinkedBlockingQueue linkedQueue
            = new LinkedBlockingQueue(capacityOfQueue);
 
        // get size of queue using size() method
        int size = linkedQueue.size();
        System.out.println("Size of Queue " + size);
 
        // Add element to LinkedBlockingQueue
        Employee emp1 = new Employee("Ranjeet", "Tester", "29000", 27);
        Employee emp2 = new Employee("Sanjeet", "Manager", "98000", 34);
        Employee emp3 = new Employee("Karan", "Analyst", "44000", 30);
 
        // Add Employee Objects to linkedQueue
        // Using put(E e)
        linkedQueue.put(emp1);
        linkedQueue.put(emp2);
        linkedQueue.put(emp3);
 
        // print details of linkedQueue
        System.out.println("\nAfter Adding some Elements queue has");
        Iterator itr = linkedQueue.iterator();
        while (itr.hasNext())
            System.out.println(itr.next());
 
        // get size of queue using size() method
        size = linkedQueue.size();
        System.out.println("\nAfter Adding Size of Queue " + size);
 
        // remove employee2 name Sanjeet and Ranjeet from linkedQueue
        linkedQueue.remove(emp2);
        linkedQueue.remove(emp1);
 
        // print details of linkedQueue
        System.out.println("\nAfter removing Some Elements");
        itr = linkedQueue.iterator();
        while (itr.hasNext())
            System.out.println(itr.next());
 
        // get size of queue using size() method
        size = linkedQueue.size();
        System.out.println("\nAfter removing size of Queue " + size);
    }
 
    // create an Employee Object with name,
    // position, salary and age as attributes
    public class Employee {
 
        public String name;
        public String position;
        public String salary;
        public int Age;
 
        Employee(String name, String position,
                 String salary, int age)
        {
            this.name = name;
            this.position = position;
            this.salary = salary;
            this.Age = age;
        }
 
        @Override
        public String toString()
        {
            return "Employee [name=" + name + ", position="
                + position + ", salary=" + salary + ", Age=" + Age + "]";
        }
    }
 
    // Main Method
    public static void main(String[] args)
    {
        GFG gfg = new GFG();
        try {
            gfg.sizeDemo();
        }
        catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

输出：

Size of Queue 0

After Adding some Elements queue has
Employee [name=Ranjeet, position=Tester, salary=29000, Age=27]
Employee [name=Sanjeet, position=Manager, salary=98000, Age=34]
Employee [name=Karan, position=Analyst, salary=44000, Age=30]

After Adding Size of Queue 3

After removing Some Elements
Employee [name=Karan, position=Analyst, salary=44000, Age=30]

After removing size of Queue 1

参考： https: Java/util/concurrent/LinkedBlockingQueue.html#size–