Java中的 BlockingQueue remainingCapacity() 方法及示例

BlockingQueue的remainingCapacity()方法返回可以在不阻塞的情况下添加到 BlockingQueue 的更多元素的数量。

返回的容量在三种情况下出现：

• 如果剩余容量为零，则不能将更多元素添加到 BlockingQueue。
• 如果 BlockingQueue 的剩余容量等于队列的大小，则无法从队列中删除任何元素，因为在这种情况下队列为空。
• 在任何其他情况下，Capacity 始终等于此 BlockingQueue 的初始容量与此 BlockingQueue 的当前大小之间的差。

句法：

public int remainingCapacity()

返回值：该方法返回BlockingQueue的剩余容量。

注意： BlockingQueue的剩余容量()方法是从Java中的Queue类继承而来的。

下面的程序说明了 BlockingQueue 类的剩余容量（）方法：

方案一：

// Java Program Demonstrate remainingCapacity()
// method of BlockingQueue
  
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.BlockingQueue;
public class GFG {
  
    public static void main(String[] args)
    {
        // define capacity of BlockingQueue
        int capacityOfQueue = 7;
  
        // create object of BlockingQueue
        BlockingQueue BQ
            = new LinkedBlockingQueue(
                capacityOfQueue);
  
        // Add element to BlockingQueue
        BQ.add("John");
        BQ.add("Tom");
        BQ.add("Clark");
        BQ.add("Kat");
  
        // find remaining Capacity  of BQ
        // using remainingCapacity() method
        int remainingCapacity
            = BQ.remainingCapacity();
  
        // print result
        System.out.println("Queue is " + BQ);
  
        // print head of the queue
        System.out.println("Remaining Capacity of Queue is "
                           + remainingCapacity);
    }
}

输出：

Queue is [John, Tom, Clark, Kat]
Remaining Capacity of Queue is 3

方案二：

// Java Program Demonstrate remainingCapacity()
// method of BlockingQueue
  
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.BlockingQueue;
public class GFG {
  
    public void findPeek()
    {
        // define capacity of BlockingQueue
        int capacityOfQueue = 7;
  
        // create object of BlockingQueue
        BlockingQueue BQ
            = new LinkedBlockingQueue(
                capacityOfQueue);
  
        // Add element to BlockingQueue
        Employee emp1
            = new Employee("Ravi", "Tester", "39000");
        Employee emp2
            = new Employee("Sanjeet", "Manager", "98000");
  
        // Add Employee Objects to BQ
        BQ.add(emp1);
        BQ.add(emp2);
  
        // add element and find remaining capacity
        // follow same process again
        // until the queue becomes full
        while (BQ.size() != 7) {
  
            // adding emp2 again and again to queue
            System.out.println(
                "Adding employee is success "
                + BQ.offer(emp2));
  
            // find remaining capacity of BQ
            // using remainingCapacity() method
            int remain = BQ.remainingCapacity();
  
            // print remaining capacity  value
            System.out.println(
                "Remaining Capacity of list :"
                + remain);
        }
    }
  
    // create an Employee Object with name,
    // position and salary as an attribute
    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 + "]";
        }
    }
  
    // Main Method
    public static void main(String[] args)
    {
        GFG gfg = new GFG();
        gfg.findPeek();
    }
}

输出：

Adding employee is success true
Remaining Capacity of list :4
Adding employee is success true
Remaining Capacity of list :3
Adding employee is success true
Remaining Capacity of list :2
Adding employee is success true
Remaining Capacity of list :1
Adding employee is success true
Remaining Capacity of list :0

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