entityMap|blocks|key|2umk4|text|首先，我的理解是，您的数据在elementData中，而size给出了存储在其中的元素的数量。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|15bnb|iterator()提供了一个迭代器。您的Iterator实现将索引作为指向当前元素的指针。|c4p1f|您计划在索引中存储什么内容？我认为有两种可能性:+a)它会给你当前的数据位置。数组中的第一个元素是元素0，因此在此之前，我会将其初始化为-1。b)它可以是可视的。因此，它首先被初始化为0，然后1表示:第一个元素，这将是elementData。==>它只是一个内部变量，所以它完全由你决定，你想在里面存储什么。|fs7h8|现在让我们来看看你的hasNext方法。如果sizer为0，则不能有下一个元素。好的。但是你要检查iterator()是否为null？迭代器总是返回内部迭代器类的新实例。所以它将永远是非空的！因此，这似乎是错误的。|2677e|你有索引和大小。所以你只需要检查索引是否已经指向最后一个元素。因此，根据上面的a/b选择，您只需检查index%2B1|dqqfs|然后是下一个函数：-它必须验证是否存在另一个元素。(=>+hasNext)+-增加索引-返回索引所指向的元素(elementDataindex或elementDataindex-1|6607t|我的提示是，用纸和笔玩弄它。只需编写一个类的实例，例如3个元素(因此elementData，elementData1，elementData2+hs一些值，大小=3。你创建一个迭代器的新实例，索引被初始化，然后看看会发生什么。|dq9u0|显示实现的一个可能的类是:导入java.util.Iterator；|a6c32|public+class+MaxHeapPriorityQueue<E+extends+Comparable<E>>+{
++++private+E[]+elementData;
++++private+int+size;

++++@SuppressWarnings("unchecked")
++++public+MaxHeapPriorityQueue()+{
++++++++elementData+=+(E[])+new+Comparable[10];
++++++++size+=+0;
++++}

++++public+void+add(E+data)+{
++++++++if+(size+==+10)+throw+new+IllegalStateException("Queue+full");

++++++++elementData[size]+=+data;
++++++++size%2B%2B;
++++}

++++public+Iterator<E>+iterator()+{
++++++++return+new+MHPQIterator();
++++}

++++public+class+MHPQIterator+implements+java.util.Iterator<E>
++++{
++++++++private+int+index=-1;

++++++++public+boolean+hasNext()
++++++++{
++++++++++++return+(index%2B1)<size;
++++++++}

++++++++public+E+next()
++++++++{
++++++++++++index%2B%2B;
++++++++++++return+elementData[index];
++++++++}
++++}

++++public+static+void+main+(String[]+args)+{
++++++++MaxHeapPriorityQueue<Integer>+queue+=+new+MaxHeapPriorityQueue<>();
++++++++Iterator<Integer>+iterator+=+queue.iterator();

++++++++System.out.println("Empty+queue:");
++++++++while+(iterator.hasNext())
++++++++++++System.out.println(iterator.next());

++++++++queue.add(1);

++++++++System.out.println("Queue+with+1+element+(1):");
++++++++iterator+=+queue.iterator();
++++++++while+(iterator.hasNext())
++++++++++++System.out.println(iterator.next());

++++++++queue.add(2);
++++++++queue.add(3);
++++++++queue.add(4);

++++++++System.out.println("Queue+with+4+elementa+(1,2,3,4):");
++++++++iterator+=+queue.iterator();
++++++++while+(iterator.hasNext())
++++++++++++System.out.println(iterator.next());
++++}
}|code-block|syntax|javascript|5qoro^0|0|0|0|0|0|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|W|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|X|9|@]|A|@]|B|$]]|$2|E|4|F|6|7|8|Y|9|@]|A|@]|B|$]]|$2|G|4|H|6|7|8|Z|9|@]|A|@]|B|$]]|$2|I|4|J|6|7|8|10|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|11|9|@]|A|@]|B|$]]|$2|M|4|N|6|7|8|12|9|@]|A|@]|B|$]]|$2|O|4|P|6|7|8|13|9|@]|A|@]|B|$]]|$2|Q|4|R|6|S|8|14|9|@]|A|@]|B|$T|U]]|$2|V|4|-4|6|7|8|15|9|@]|A|@]|B|$]]]]

First of all, my understanding is, that your data is inside elementData and size gives the number of elements stored inside.

iterator() gives you an iterator. Your Iterator implementation has index as a point to the current element.

What do you plan to store inside index? I see 2 possibilities:
a) it is giving you the current data location. The first element inside the array is element 0, so to be before that, I would initialize it as -1.
b) It could be visual. So it is initialized as 0 first and then 1 means: first element, which would be the elementData[0].
==> It is just an internal variable so it is completely up to you, what you want to store inside of it.

Now let us look at your hasNext method. If the sizer is 0, then there cannot be a next element. Ok. But then you check if iterator() is null? iterator always returns a new instance of your inner iterator class. So it will always be non null! So this seems wrong.

You have index and size. So you just have to check if the index is already pointing to the last element. So depending on the choice a/b above, you simply have to check if index+1 &lt; size or index

And then the next function:
 - It has to validate that there is another element. (=> hasNext)
 - you increase index
 - you return the element, index is pointing to (elementData[index] or elementData[index-1] (depends again on your decision what to store inside index)

My hint is, to play around with it with paper and pen. Just write an instance of your class with e.g. 3 elements (so elementData[0], elementData[1], elementData[2] hs some value, size = 3. You create a new instance of your iterator, index is initialized and then see what must happen.

A possible class that shows an implementation is:
import java.util.Iterator;

<pre><code>public class MaxHeapPriorityQueue&lt;E extends Comparable&lt;E&gt;&gt; {
 private E[] elementData;
 private int size;

 @SuppressWarnings("unchecked")
 public MaxHeapPriorityQueue() {
 elementData = (E[]) new Comparable[10];
 size = 0;
 }

 public void add(E data) {
 if (size == 10) throw new IllegalStateException("Queue full");

 elementData[size] = data;
 size++;
 }

 public Iterator&lt;E&gt; iterator() {
 return new MHPQIterator();
 }

 public class MHPQIterator implements java.util.Iterator&lt;E&gt;
 {
 private int index=-1;

 public boolean hasNext()
 {
 return (index+1)&lt;size;
 }

 public E next()
 {
 index++;
 return elementData[index];
 }
 }

 public static void main (String[] args) {
 MaxHeapPriorityQueue&lt;Integer&gt; queue = new MaxHeapPriorityQueue&lt;&gt;();
 Iterator&lt;Integer&gt; iterator = queue.iterator();

 System.out.println("Empty queue:");
 while (iterator.hasNext())
 System.out.println(iterator.next());

 queue.add(1);

 System.out.println("Queue with 1 element (1):");
 iterator = queue.iterator();
 while (iterator.hasNext())
 System.out.println(iterator.next());

 queue.add(2);
 queue.add(3);
 queue.add(4);

 System.out.println("Queue with 4 elementa (1,2,3,4):");
 iterator = queue.iterator();
 while (iterator.hasNext())
 System.out.println(iterator.next());
 }
}
</code></pre>

entityMap|blocks|key|ej9ge|text|如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|6qr1n|public+class+MHPQIterator+implements+java.util.Iterator<E>
{
++++private+int+index=0;

++++public+boolean+hasNext()
++++{
++++++++return+(index+<+size);
++++}
++++public+E+next()
++++{
++++++++return+elementData[index%2B%2B];
++++}
}|code-block|syntax|javascript|7tesn^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|I|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|J|9|@]|A|@]|B|$F|G]]|$2|H|4|-4|6|7|8|K|9|@]|A|@]|B|$]]]]

Like this:

<pre><code>public class MHPQIterator implements java.util.Iterator&lt;E&gt;
{
 private int index=0;

 public boolean hasNext()
 {
 return (index &lt; size);
 }
 public E next()
 {
 return elementData[index++];
 }
}
</code></pre>

entityMap|blocks|key|1pe63|text|以下是对我有效的方法，然而答案被张贴在这里，我接受了它，但这是对我的代码有效的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3bgfp|public+class+MHPQIterator+implements+java.util.Iterator<E>
{
++++private+int+index;

++++public+boolean+hasNext()
++++{
++++++++if(size+==+0)
++++++++{
++++++++++++return+false;
++++++++}
++++++++else
++++++++{
++++++++++++return+(index+<+size);
++++++++}
++++}
++++public+E+next()
++++{
++++++++index%2B%2B;
++++++++return+elementData[index];
++++}
}|code-block|syntax|javascript|bf48^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|I|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|J|9|@]|A|@]|B|$F|G]]|$2|H|4|-4|6|7|8|K|9|@]|A|@]|B|$]]]]

Here is what worked for me, however the answer was posted here and I accepted it, but here's what worked with my code. 

<pre><code>public class MHPQIterator implements java.util.Iterator&lt;E&gt;
{
 private int index;

 public boolean hasNext()
 {
 if(size == 0)
 {
 return false;
 }
 else
 {
 return (index &lt; size);
 }
 }
 public E next()
 {
 index++;
 return elementData[index];
 }
}
</code></pre>

I need help writing this next() method in this class. I've tried several stuff, but I keep getting that I'm not returning the next value, but rather null. 

The instructions for this class reads: This class should be public, non-static, and should implement java.util.Iterator. It's index instance variable should be initialized with an appropriate value. It's hasNext() method should return true if any elements in the queue have yet to be returned by its next() method. It's next() method should return queue values in the same order as in the underlying array.

Therefore I'm going to write the code that I have, but will cut it short so only the important elements that are relatable to my problem shows. 

<pre><code>public class MaxHeapPriorityQueue&lt;E extends Comparable&lt;E&gt;&gt;
{
private E[] elementData;
private int size;

@SuppressWarnings("unchecked")
public MaxHeapPriorityQueue()
{
 elementData = (E[]) new Comparable[10];
 size = 0;
}
public Iterator&lt;E&gt; iterator()
{
 return new MHPQIterator();
}
</code></pre>

and the other class takes place here, which has ties with the Iterator method. 

<pre><code>public class MHPQIterator implements java.util.Iterator&lt;E&gt;
{
 private int index;

 public boolean hasNext()
 {
 if(size == 0)
 {
 return false;
 }
 else
 {
 return (index &lt; size);
 }
 }
 public E next()
 {
 return elementData[index];
 }
}
</code></pre>

I'm not sure if I'm elementData would work, but I don't know what else I could return with.

How to write a next method with an Iterator and a MaxHeapPriorityQueue in java

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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 我需要在这个类中编写next()方法的帮助。我已经尝试了几种方法，但我总是发现返回的不是下一个值，而是null。 该类的说明为:该类应该是公共的、非静态的，并且应该实现java.util.Iterator。它的index实例变量应该使用适当的值进行初始化。如果它的hasNext()方法还没有返回队列中的任何元素，那么...

问如何在java中编写带有迭代器和MaxHeapPriorityQueue的next方法
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问如何在java中编写带有迭代器和MaxHeapPriorityQueue的next方法EN