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Java Deque contains()用法及代码示例


Deque接口的contains(E e)方法检查Deque容器中元素e的存在。如果双端队列包含元素的一次出现，则返回true，否则返回false。

用法:

boolean contains(Object o)

参数：此方法接受强制性参数o，该参数是是否需要在Deque中进行测试的元素。


返回值：如果元素存在于双端队列中，则该方法返回True，否则返回False。

异常：该函数引发两个异常，如下所示：

  • ClassCastException–如果指定元素的类型与此双端队列不兼容。它是可选的。
  • NullPointerException –如果指定的元素为null，并且此双端队列不允许使用null元素(可选)。它是可选的。

以下程序说明了Java中的contains()方法：

示例1:借助LinkedList。

// Java code to illustrate contains() 
// method of Deque in Java 
import java.util.*; 
  
public class GFG { 
    public static void main(String args[]) 
    { 
        // Creating an empty Deque 
        Deque<String> de_que = new LinkedList<String>(); 
  
        // Use add() method to add elements into the Queue 
        de_que.add("Welcome"); 
        de_que.add("To"); 
        de_que.add("Geeks"); 
        de_que.add("4"); 
        de_que.add("Geeks"); 
  
        // Displaying the Deque 
        System.out.println("Deque: " + de_que); 
  
        // Check for "Geeks" in the deque 
        System.out.println("Does the deque contains 'Geeks'? "
                           + de_que.contains("Geeks")); 
  
        // Check for "4" in the deque 
        System.out.println("Does the deque contains '4'? "
                           + de_que.contains("4")); 
  
        // Check if the deque contains "No" 
        System.out.println("Does the deque contains 'No'? "
                           + de_que.contains("No")); 
    } 
}
输出： 
Deque: [Welcome, To, Geeks, 4, Geeks]
Does the deque contains 'Geeks'? true
Does the deque contains '4'? true
Does the deque contains 'No'? false

示例2: 

// Java code to illustrate contains() 
// method of Deque in Java 
import java.util.*; 
  
public class GFG { 
    public static void main(String args[]) 
    { 
        // Creating an empty Deque 
        Deque<Integer> de_que = new LinkedList<Integer>(); 
  
        // Use add() method to add elements into the Queue 
        de_que.add(10); 
        de_que.add(15); 
        de_que.add(30); 
        de_que.add(20); 
        de_que.add(5); 
  
        // Displaying the Deque 
        System.out.println("Deque: " + de_que); 
  
        // Check for '15' in the Deque 
        System.out.println("Does the Deque contains '15'? "
                           + de_que.contains(15)); 
  
        // Check for '2' in the Deque 
        System.out.println("Does the Deque contains '2'? "
                           + de_que.contains(2)); 
  
        // Check if the Deque contains '10' 
        System.out.println("Does the Deque contains '10'? "
                           + de_que.contains(10)); 
    } 
}
输出： 
Deque: [10, 15, 30, 20, 5]
Does the Deque contains '15'? true
Does the Deque contains '2'? false
Does the Deque contains '10'? true

示例3:借助ArrayDeque。

// Java code to illustrate contains() 
// method of Deque in Java 
import java.util.*; 
  
public class GFG { 
    public static void main(String args[]) 
    { 
        // Creating an empty Deque 
        Deque<Integer> de_que = new ArrayDeque<Integer>(); 
  
        // Use add() method to add elements into the Queue 
        de_que.add(10); 
        de_que.add(15); 
        de_que.add(30); 
        de_que.add(20); 
        de_que.add(5); 
  
        // Displaying the Deque 
        System.out.println("Deque: " + de_que); 
  
        // Check for '15' in the Deque 
        System.out.println("Does the Deque contains '15'? "
                           + de_que.contains(15)); 
  
        // Check for '2' in the Deque 
        System.out.println("Does the Deque contains '2'? "
                           + de_que.contains(2)); 
  
        // Check if the Deque contains '10' 
        System.out.println("Does the Deque contains '10'? "
                           + de_que.contains(10)); 
    } 
}
输出： 
Deque: [10, 15, 30, 20, 5]
Does the Deque contains '15'? true
Does the Deque contains '2'? false
Does the Deque contains '10'? true

示例4:借助ConcurrentLinkedDeque。

// Java code to illustrate contains() 
// method of Deque in Java 
import java.util.*; 
import java.util.concurrent.ConcurrentLinkedDeque; 
  
public class GFG { 
    public static void main(String args[]) 
    { 
        // Creating an empty Deque 
        Deque<Integer> de_que = new ConcurrentLinkedDeque<Integer>(); 
  
        // Use add() method to add elements into the Queue 
        de_que.add(10); 
        de_que.add(15); 
        de_que.add(30); 
        de_que.add(20); 
        de_que.add(5); 
  
        // Displaying the Deque 
        System.out.println("Deque: " + de_que); 
  
        // Check for '15' in the Deque 
        System.out.println("Does the Deque contains '15'? "
                           + de_que.contains(15)); 
  
        // Check for '2' in the Deque 
        System.out.println("Does the Deque contains '2'? "
                           + de_que.contains(2)); 
  
        // Check if the Deque contains '10' 
        System.out.println("Does the Deque contains '10'? "
                           + de_que.contains(10)); 
    } 
}
输出： 
Deque: [10, 15, 30, 20, 5]
Does the Deque contains '15'? true
Does the Deque contains '2'? false
Does the Deque contains '10'? true

示例5:借助LinkedBlockingDeque。

// Java code to illustrate contains() 
// method of Deque in Java 
import java.util.*; 
import java.util.concurrent.LinkedBlockingDeque; 
  
public class GFG { 
    public static void main(String args[]) 
    { 
        // Creating an empty Deque 
        Deque<Integer> de_que = new LinkedBlockingDeque<Integer>(); 
  
        // Use add() method to add elements into the Queue 
        de_que.add(10); 
        de_que.add(15); 
        de_que.add(30); 
        de_que.add(20); 
        de_que.add(5); 
  
        // Displaying the Deque 
        System.out.println("Deque: " + de_que); 
  
        // Check for '15' in the Deque 
        System.out.println("Does the Deque contains '15'? "
                           + de_que.contains(15)); 
  
        // Check for '2' in the Deque 
        System.out.println("Does the Deque contains '2'? "
                           + de_que.contains(2)); 
  
        // Check if the Deque contains '10' 
        System.out.println("Does the Deque contains '10'? "
                           + de_que.contains(10)); 
    } 
}
输出： 
Deque: [10, 15, 30, 20, 5]
Does the Deque contains '15'? true
Does the Deque contains '2'? false
Does the Deque contains '10'? true

注意：这些异常取决于编译器，因此无法在程序中显示。
参考： https://docs.oracle.com/javase/8/docs/api/java/util/Deque.html#contains-java.lang.Object-



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注：本文由纯净天空筛选整理自gopaldave大神的英文原创作品 Deque contains() method in Java。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。