Java Deque contains()方法

Deque接口的 contains(E e) 方法检查Deque容器中是否存在元素e。如果Deque中包含一个元素，那么它就会返回true，否则就会返回false。

语法

boolean contains(Object o)

参数： 该方法接受一个强制参数o，即需要测试的元素是否存在于Deque中。

返回值： 如果该元素存在于Deque中，该方法返回True，否则返回False。

异常： 该函数抛出两个异常，如下所示。

下面的程序说明了Java中的contains()方法。

程序1： 在 LinkedList 的帮助下 。

// Java code to illustrate contains()// method of Deque in Javaimport 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'? trueDoes the deque contains '4'? trueDoes the deque contains 'No'? false

程序2

// Java code to illustrate contains()// method of Deque in Javaimport 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'? trueDoes the Deque contains '2'? falseDoes the Deque contains '10'? true

程序3： 在 ArrayDeque 的帮助下 。

// Java code to illustrate contains()// method of Deque in Javaimport 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'? trueDoes the Deque contains '2'? falseDoes the Deque contains '10'? true

程序4： 在 ConcurrentLinkedDeque 的帮助下 。

// Java code to illustrate contains()// method of Deque in Javaimport 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'? trueDoes the Deque contains '2'? falseDoes the Deque contains '10'? true

程序5： 在 LinkedBlockingDeque 的帮助下 。

// Java code to illustrate contains()// method of Deque in Javaimport 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'? trueDoes the Deque contains '2'? falseDoes the Deque contains '10'? true

注意： 例外情况取决于编译器，因此不能在程序中显示。
参考资料 ：https://docs.oracle.com/javase/8/docs/api/java/util/Deque.html#contains-java.lang.Object-