我需要帮助我的自定义链表，我无法弄清楚问题。需要一些帮助。 这是我的size（）方法：
public ObjectLinkedList() {
firstNode = null;
}
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Method: add() description: Insert an item into the list
*
* @param index position of the list
* @param obj the element is going to be inserted
* @author Jinyu Wu Date: 2017/2/4
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
@Override
public void add(int index, Object obj) {
Node tempNode = firstNode;
Node currentNode = new Node(obj);
if (index == 0) {
firstNode = currentNode;
return;
}
if (index < 0 || index > size()) {
System.out.println("add(ObjectLinkedList) index out of bound exception");
} else {
for (int i = 1; i <= index; i++) {
tempNode = tempNode.getNext();
if (i == index - 1) {
if (index != size() - 1) {
currentNode.setNext(tempNode.getNext());
} else {
currentNode.setNext(null);
}
tempNode.setNext(currentNode);
}
}
}
}
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Method: removeAt() description: remove an item from a position of the
* list
*
* @param index position in the list
* @author Jinyu Wu Date: 2017/2/4
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
@Override
public void removeAt(int index) {
if (index < 0 || index > size()) {
System.out.println("removeAt(ObjectLinkedList) index out of bound exception");
} else {
Node tempNode = firstNode;
if (index == 0) {
firstNode = firstNode.getNext();
} else {
for (int i = 1; i <= index; i++) {
if (i == index - 1) {
if (index != size() - 1) {
tempNode.setNext(tempNode.getNext().getNext());
} else {
tempNode.setNext(null);
}
}
tempNode = tempNode.getNext();
}
}
}
}
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Method: remove() description: remove a specific item from a position of
* the list
*
* @param obj target object is going to be removed
* @author Jinyu Wu Date: 2017/2/4
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
@Override
public void remove(Object obj) {
if (size() > 0) {
Node tempNode = firstNode;
for (int i = 0; i <= size(); i++) {
if (tempNode.equals(obj)) {
tempNode.setNext(tempNode.getNext().getNext());
break;
}
if (i < size() - 1) {
tempNode = tempNode.getNext();
}
}
System.out.println("target object is not found inside the linkedList(remove)");
}
}
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Method: get() description:get an item from the list
*
* @param index position in the list
* @author Jinyu Wu Date: 2017/2/4
* @return double ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
@Override
public Object get(int index) {
if (index < 0 || index > size()) {
System.out.println("get(ObjectLinkedList) index out of bound exception");
return null;
} else if (index == 0) {
return firstNode.getValue();
} else {
Node tempNode = firstNode;
for (int i = 0; i <= index; i++) {
if (i == index - 1) {
return tempNode.getValue();
}
tempNode = tempNode.getNext();
}
System.out.println("objectLinkedList get method nothing found");
return null;
}
}
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Method: toString() description: print out the content of the list
*
* @author Jinyu Wu Date: 2017/2/4
* @return Integer ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
@Override
public String toString() {
Node tmp = firstNode;
String res = "" + firstNode;
while (tmp.getNext() != null) {
tmp = tmp.getNext();
res += "," + tmp;
}
return "ObjectLinkedList{" + res + "}";
}
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Method: find() description:get an item from the list
*
* @author Jinyu Wu Date: 2017/2/4
* @param obj Object is going to be found
* @return Integer ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
@Override
public int find(Object obj) {
Node tempNode = firstNode;
if (obj.equals(firstNode.getValue())) {
return 0;
} else {
for (int i = 1; i < size(); i++) {
tempNode = tempNode.getNext();
if (tempNode.getValue().equals(obj)) {
return i;
}
}
return -1;
}
}
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Method: size() description:get the size of the list
*
* @author Jinyu Wu Date: 2017/2/4
* @return Integer ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
@Override
public int size() {
int size = 1;
if (firstNode == null) {
return 0;
}
try {
for (Node n = firstNode; n.getNext() != null; n = n.getNext()) {
size++;
}
return size;
} catch (NullPointerException e) {
return size;
}
}
这是我的Node类：
public class Node {
private Node nextNode;
private Object obj;
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Method: Node() description: constructor
*
* @author Jinyu Wu Date: 2017/2/4
* @param obj set the value
*/
public Node(Object obj) {
this.obj = obj;
this.nextNode = null;
}
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Method: getValue() description: get the value of object
*
* @author Jinyu Wu Date: 2017/2/4
* @return return the object
*/
public Object getValue() {
return this.obj;
}
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Method: setValue() description: setValue for the Node
*
* @author Jinyu Wu Date: 2017/2/4
* @param obj return the value
*/
public void setValue(Object obj) {
this.obj = obj;
}
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Method: getValue() description: get the next value of the currentNode
*
* @author Jinyu Wu Date: 2017/2/4
* @return return next node
*/
public Node getNext() {
if (nextNode != null) {
return this.nextNode;
} else {
return null;
}
}
/**
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Method: setNext() description: set next value for the Node
*
* @author Jinyu Wu Date: 2017/2/4
* @param node set next node
*/
public void setNext(Node node) {
this.nextNode = node;
}
}
我的大小编号一直不正确，但我无法弄清楚问题。
这是我在main方法中的代码：
list = new ObjectLinkedList();
m1 = new Money(5, (byte) 6);
node1 = new Node(m1);
list.add(0, node1);
m2 = new Money(2, (byte) 4);
node2 = new Node(m2);
list.add(1, node2);
System.out.println(list.Size());
我一直得到1而不是2;
答案 0 :(得分：0)
在size：
ObjectLinkedList字段
private int size;
在添加新项目之前在行中增加它，并在从列表中删除项目之前将其减少到行中。
然后只需添加一个方法：
public int getSize() {
return this.size;
}
由于OP要求发布递归方法（这是低效的！）：
public int size(ObjectLinkedList list) {
if (list.firstNode == null)
return 0;
return 1 + size(list.firstNode.getNext());
}
答案 1 :(得分：0)
错误存在于add(int, Object)方法中，更确切地说，位于以下构造中：
for (int i = 1; i <= index; i++) {
tempNode = tempNode.getNext();
if (i == index - 1) {
if (index != size() - 1) {
currentNode.setNext(tempNode.getNext());
} else {
currentNode.setNext(null);
}
tempNode.setNext(currentNode);
}
}
第二次向列表中添加资金时，请致电list.add(1, node2)。但是，从index = 1开始i和1递增，i == index - 1永远不会是true。
因此，第二个对象根本没有插入到您的列表中。您可以通过调用toString()方法进行检查。
我猜你这样做if - 子句，因为你希望嵌套在里面的代码仅在tempNode是你正在寻找的时才执行。但是，通过将代码放在for - 循环后面并使用其条件，您可以更轻松地完成此操作：
for(int i = 1; i < index; i++) {
tempNode = tempNode.getNext();
}
if(index != size() - 1) {
currentNode.setNext(tempNode.getNext());
}
// we just created this node, so we can be quite sure that it does not have a next node set
// else {
// currentNode.setNext(null);
// }
tempNode.setNext(currentNode);
您的列表已经包含了Node中的对象，因此您无需在main方法中执行此操作。因此，而不是
list = new ObjectLinkedList();
m1 = new Money(5, (byte) 6);
node1 = new Node(m1);
list.add(0, node1);
m2 = new Money(2, (byte) 4);
node2 = new Node(m2);
list.add(1, node2);
System.out.println(list.size());
你应该能够写
list = new ObjectLinkeList();
m1 = new Money(5, (byte) 6);
list.add(m1);
m2 = new Money(2, (byte) 4);
list.add(m2);
System.out.println(list.size());
或只是
list = new ObjectLinkeList();
list.add(new Money(5, (byte) 6));
list.add(new Money(2, (byte) 4));
System.out.println(list.size());
答案 2 :(得分：0)
获取链表的大小就是遍历它。下面我提供了三个遍历链表的选项：for循环，while循环和递归。
class ObjectLinkedList<T> {
public static void main(String... args) {
final ObjectLinkedList<String> list = new ObjectLinkedList<>();
list.add(0, "World");
list.add(0, "Hello");
list.add(2, "!");
System.out.println(list);
System.out.println(list.size());
}
private Node<T> firstNode = null;
public void add(int index, T obj) {
final Node<T> newNode = new Node<>(obj);
Node<T> tempNode = firstNode;
if (index == 0) {
firstNode = newNode;
firstNode.setNext(tempNode);
return;
} else {
int count = 0;
//option 1: a for loop
for (Node<T> current = firstNode; current != null; current = current.getNext()) {
tempNode = current.getNext();
if (++count == index) {
current.setNext(newNode);
newNode.setNext(tempNode);
return;
}
}
}
throw new IndexOutOfBoundsException("Out of bounds!");
}
public String toString() {
Node<T> tmp = firstNode;
StringBuilder res = new StringBuilder("ObjectLinkedList: [");
//option 2: a while loop
while (tmp != null) {
res.append(tmp);
tmp = tmp.getNext();
if (tmp != null) {
res.append(", ");
}
}
return res.append("]").toString();
}
public int size() {
return distanceFromEnd(firstNode);
}
//option 3: recursion
private int distanceFromEnd(Node<T> startingNode) {
if (startingNode == null) {
return 0;
} else {
return 1 + distanceFromEnd(startingNode.getNext());
}
}
}
class Node<T> {
private Node<T> next = null;
final private T value;
public Node(final T value) {
assert value != null;
this.value = value;
}
public Node<T> getNext() {
return next;
}
public void setNext(final Node<T> next) {
this.next = next;
}
public T getValue() {
return value;
}
@Override
public String toString() {
return value.toString();
}
}