Java Deque descendingIterator()方法

Deque接口的 descendingIterator(E e) 方法以相反的顺序返回该deque中元素的迭代器。这些元素将按照从最后（尾部）到第一个（头部）的顺序返回。返回的迭代器是一个 “弱一致性 “迭代器。

语法

Iterator descendingIterator()

参数： 该方法不接受任何参数。

返回值： 该方法以适当的顺序返回该deque中的元素的迭代器。

以下程序说明了Java中的descendingIterator()方法。

程序1： 在 LinkedList 的帮助下 。

// Java code to illustrate descendingIterator()// 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");          // Call iterator() method of deque        Iterator iteratorVals = de_que.iterator();          // Print elements of iterator        // created from PriorityBlockingQueue        System.out.println("The iterator values"                           + " of deque are:");          // prints the elements using an iterator        while (iteratorVals.hasNext()) {            System.out.println(iteratorVals.next());        }    }}

输出:

The iterator values of deque are:WelcomeToGeeks4Geeks

程序2

// Java code to illustrate descendingIterator()// 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);          // Call iterator() method of deque        Iterator iteratorVals = de_que.iterator();          // Print elements of iterator        // created from PriorityBlockingQueue        System.out.println("The iterator values"                           + " of deque are:");          // prints the elements using an iterator        while (iteratorVals.hasNext()) {            System.out.println(iteratorVals.next());        }    }}

输出:

The iterator values of deque are:101530205

程序3： 在 ArrayDeque 的帮助下 。

// Java code to illustrate descendingIterator()// 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 ArrayDeque<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");          // Call iterator() method of deque        Iterator iteratorVals = de_que.iterator();          // Print elements of iterator        // created from PriorityBlockingQueue        System.out.println("The iterator values"                           + " of deque are:");          // prints the elements using an iterator        while (iteratorVals.hasNext()) {            System.out.println(iteratorVals.next());        }    }}

输出:

The iterator values of deque are:WelcomeToGeeks4Geeks

程序4： 在 LinkedBlockingDeque 的帮助下 。

// Java code to illustrate descendingIterator()// 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<String> de_que = new LinkedBlockingDeque<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");          // Call iterator() method of deque        Iterator iteratorVals = de_que.iterator();          // Print elements of iterator        // created from PriorityBlockingQueue        System.out.println("The iterator values"                           + " of deque are:");          // prints the elements using an iterator        while (iteratorVals.hasNext()) {            System.out.println(iteratorVals.next());        }    }}

输出:

The iterator values of deque are:WelcomeToGeeks4Geeks

程序5： 在 ConcurrentLinkedDeque 的帮助下 。

// Java code to illustrate descendingIterator()// 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<String> de_que = new ConcurrentLinkedDeque<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");          // Call iterator() method of deque        Iterator iteratorVals = de_que.iterator();          // Print elements of iterator        // created from PriorityBlockingQueue        System.out.println("The iterator values"                           + " of deque are:");          // prints the elements using an iterator        while (iteratorVals.hasNext()) {            System.out.println(iteratorVals.next());        }    }}

输出:

The iterator values of deque are:WelcomeToGeeks4Geeks

参考资料: https://docs.oracle.com/javase/8/docs/api/java/util/Deque.html#descendingIterator-