Java中的双端队列 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。如果双端队列包含一个元素，则返回 true，否则返回 false。
句法：
boolean contains(Object o)参数：此方法接受一个强制参数 o，它是需要测试的元素是否存在于 Deque 中。
返回值：如果元素存在于 Deque 中，则该方法返回True ，否则返回False。
异常：该函数抛出两个异常，如下所示：
- 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 – 如果指定元素为 null 并且此 Deque 不允许 null 元素（可选）。它是可选的。
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 Java
import java.util.*;
public class GFG {
public static void main(String args[])
{
// Creating an empty Deque
Deque de_que = new LinkedList();
// 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
方案二：
// 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 de_que = new LinkedList();
// 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
程序 3：在ArrayDeque的帮助下。
// 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 de_que = new ArrayDeque();
// 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
程序 4：在ConcurrentLinkedDeque的帮助下。
// 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 de_que = new ConcurrentLinkedDeque();
// 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
程序 5：在LinkedBlockingDeque的帮助下。
// 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 de_que = new LinkedBlockingDeque();
// 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：异常取决于编译器，因此无法在程序中显示。
参考： https: Java/util/Deque.html#contains-java.lang.Object-