我创建了一个自定义链接列表。我还为其制作了一个迭代器。但据我了解,程序不会在方法 size() 中进入循环。它出什么问题了?是因为我的循环或迭代器()不正确吗?每个节点都有字段:nextIndex
、prevIndex
、value
。
public class CustomLinkedList<E> implements List<E>{
private ListNode<E> header = new ListNode<>();
public CustomLinkedList() {
this.header = new ListNode();
}
@Override
public int size() {
int size = 0;
for(E it : this) {
size++;
}
return size;
}
@Override
public boolean isEmpty() {
if(this.header == null){
return true;
} else {return false;}
}
@Override
public boolean contains(Object o) {
if(((Integer) header.getValue() == 42) && ((Integer) header.getNextIndex().getValue() == 38)) return true;
return false;
}
@Override
public Iterator<E> iterator() {
return new Iterator<E>() {
private ListNode it = header;
@Override
public boolean hasNext() {
return (it.getNextIndex() != header) && (it.getNextIndex() != null);
}
@Override
public E next() {
it = it.getNextIndex();
return (E) it.getValue();
}
@Override
public void remove()
{
throw new UnsupportedOperationException("Iterator is read-only");
}
};
}
@Override
public boolean add(E e) {
ListNode<E> temp = new ListNode<>();
temp.setValue(e);
if (this.size() < 1) {
header.setValue(e);
header.setPrevIndex(header);
header.setNextIndex(header);
} else {
temp.setNextIndex(header);
ListNode tempLast = header.getPrevIndex();
tempLast.setNextIndex(temp);
header.setPrevIndex(temp);
temp.setPrevIndex(tempLast);
}
return true;
}
@Override
public boolean remove(Object o) {
return true;
}
@Override
public boolean containsAll(Collection<?> c) {
throw new NotImplementedException();
}
@Override
public void clear() {
throw new NotImplementedException();
}
@Override
public E get(int index) {
throw new NotImplementedException();
}
@Override
public int indexOf(Object o) {
throw new NotImplementedException();
}
@Override
public boolean addAll(Collection<? extends E> c) {
throw new NotImplementedException();
}
}
最佳答案
从 header.getNextIndex() == null
开始,然后调用 add(E e)
一次。
在 add()
内部,size()
将返回 0,因此您设置 header.setPrevIndex(header)
和 header.setNextIndex(header )
接下来再次调用add(E e)
。在
add()内部,
size()将调用
hasNext()并且
hasNext()将检查(it. getNextIndex() != header) && (it.getNextIndex() != null)
这将返回 false 因为 it.getNextIndex() == header
因此 size()
将始终小于 1。
您的代码中还有很多其他错误。更好的部分实现类似于
public class CustomLinkedList<E> implements List<E> {
private ListNode<E> header;
public CustomLinkedList() {
this.header = null;
}
@Override
public int size() {
int size = 0;
for (E it : this)
size++;
return size;
}
@Override
public boolean isEmpty() {
return header == null;
}
@Override
public boolean contains(Object obj) {
if (header != null)
for (E it : this)
if (it.equals(obj))
return true;
return false;
}
@Override
public Iterator<E> iterator() {
return new Iterator<E>() {
private ListNode<E> it = null;
@Override
public boolean hasNext() {
if (it==null && header!=null)
return true;
else if (it != null)
return it.getNextIndex() != null;
else
return false;
}
@Override
public E next() {
if (it==null)
it = header;
else
it = it.getNextIndex();
return it.getValue();
}
@Override
public void remove() {
throw new UnsupportedOperationException("Iterator is read-only");
}
};
}
@Override
public boolean add(E e) {
ListNode<E> temp = new ListNode<>();
temp.setValue(e);
if (header == null) {
header = temp;
} else {
ListNode<E> it = header;
while (it.getNextIndex() != null)
it = it.getNextIndex();
temp.setPrevIndex(it);
it.setNextIndex(temp);
}
return true;
}
}
关于java - 链表的自定义迭代器,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/42607100/