Java中的 LinkedBlockingQueue contains() 方法

如果队列包含作为参数传递的对象 obj，LinkedBlockingQueue 的contains(Object obj)方法将返回 true。当且仅当此队列包含至少一个等于作为参数 ieeequals(o) 传递的对象 o 的元素 e 时，它才返回 true。这个方法对于检查队列是否有元素非常有帮助。

句法：

public boolean contains(Object o)

参数：此方法需要一个强制参数o ，它是队列中要检查的对象。

返回值：如果此队列包含作为参数传递的对象，则此方法返回true 。否则返回false 。

下面的程序说明了 LinkedBlockingQueue 类的 contains() 方法：

程序1：检查数字队列中是否包含数字n。数字 n 作为输入传递给 LinkedBlockingQueue 的 contains()。

// Java Program Demonstrate contains(Object o)
// method of LinkedBlockingQueue
  
import java.util.concurrent.LinkedBlockingQueue;
  
public class GFG {
  
    public static void main(String[] args)
    {
        // define capacity of LinkedBlockingQueue
        int capacityOfQueue = 50;
  
        // create object of LinkedBlockingQueue
        LinkedBlockingQueue linkedQueue
            = new LinkedBlockingQueue(capacityOfQueue);
  
        // Add element to LinkedBlockingQueue
        linkedQueue.add(2300);
        linkedQueue.add(1322);
        linkedQueue.add(8945);
        linkedQueue.add(6512);
  
        // print LinkedQueue
        System.out.println("linkedQueue: " + linkedQueue);
  
        // check whether LinkedBlockingQueue contains 6512
        boolean response1 = linkedQueue.contains(6512);
  
        // print result
        System.out.println("LinkedBlockingQueue contains "
                           + "number 6512 : "
                           + response1);
  
        // check whether LinkedBlockingQueue contains 5324
        boolean response2 = linkedQueue.contains(5324);
  
        // print result
        System.out.println("LinkedBlockingQueue contains"
                           + " number 5324 : "
                           + response2);
    }
}

输出：

linkedQueue: [2300, 1322, 8945, 6512]

LinkedBlockingQueue contains number 6512 : true
LinkedBlockingQueue contains number 5324 : false

程序2：检查一个雇员队列中是否包含某个雇员e。员工 e 的详细信息作为输入传递给 LinkedBlockingQueue 的 contains()。

// Java Program Demonstrate contains(Object o)
// method of LinkedBlockingQueue.
  
import java.util.concurrent.LinkedBlockingQueue;
  
public class GFG {
  
    // create an Employee Object with
    // 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.containsMethodExample();
    }
  
    public void containsMethodExample()
    {
  
        // define capacity of LinkedBlockingQueue
        int capacity = 50;
  
        // create object of LinkedBlockingQueue
        LinkedBlockingQueue linkedQueue
            = new LinkedBlockingQueue(capacity);
  
        Employee emp1 = new Employee("Aman",
                                     "Analyst",
                                     "24000");
        Employee emp2 = new Employee("Sachin",
                                     "Developer",
                                     "39000");
  
        // Add Employee Objects to linkedQueue
        linkedQueue.add(emp1);
        linkedQueue.add(emp2);
  
        // print LinkedQueue
        System.out.println("linkedQueue: " + linkedQueue);
  
        // Employee to be checked
        Employee checkEmp1 = new Employee("Sanjeev",
                                          "Tester",
                                          "26000");
  
        // check whether linkedQueue contains emp1
        boolean response1 = linkedQueue.contains(emp1);
  
        // print results
        System.out.println("linkedQueue contains "
                           + emp1.toString() + " : "
                           + response1);
  
        // check whether linkedQueue contains checkEmp1
        boolean response2 = linkedQueue.contains(checkEmp1);
  
        // print results
        System.out.println("linkedQueue contains "
                           + checkEmp1.toString() + " : "
                           + response2);
    }
}

输出：

linkedQueue: 
[Employee [name=Aman, position=Analyst, salary=24000], 
Employee [name=Sachin, position=Developer, salary=39000]]

linkedQueue contains Employee [name=Aman, position=Analyst, salary=24000] : true
linkedQueue contains Employee [name=Sanjeev, position=Tester, salary=26000] : false

参考：
https://docs.oracle.com/javase/8/docs/api/java Java