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[英]Can someone tell me what I'm doing wrong to setup this Robot class in Java?
[英]Can someone tell me what i'm doing wrong? Counting and looping through LinkedList
我的代码如下:
import net.datastructures.Node;
public class SLinkedListExtended<E> extends SLinkedList<E> {
public int count(E elem) {
Node <E> currentNode = new Node <E>();
currentNode = head;
int counter = 0;
for (int i = 0; i<size; i++){
if (currentNode == null) {
return 0; //current is null
}
else if (elem.equals(currentNode.getElement())){
counter++;
currentNode = currentNode.getNext();
}
}
return counter;
}
public static void main(String[] args) {
SLinkedListExtended<String> x = new SLinkedListExtended<String>();
x.insertAtTail("abc");
x.insertAtTail("def");
x.insertAtTail("def");
x.insertAtTail("xyz");
System.out.println(x.count("def")); // should print "2"
//x.insertAtTail(null);
x.insertAtTail("def");
//x.insertAtTail(null);
System.out.println(x.count("def")); // should print "3"
//System.out.println(x.count(null)); // should print "2"
}
}
方法计数应该返回给定元素elem在列表中找到的次数。 我已经编写了这个循环,但每次只返回0。 还会抛出nullpointerexception。
编辑:SLinkedList SuperClass
import net.datastructures.Node;
public class SLinkedList<E> {
protected Node<E> head; // head node of the list
protected Node<E> tail; // tail node of the list (if needed)
protected long size; // number of nodes in the list (if needed)
// default constructor that creates an empty list
public SLinkedList() {
head = null;
tail = null;
size = 0;
}
// update and search methods
public void insertAtHead(E element) {
head = new Node<E>(element, head);
size++;
if (size == 1) {
tail = head;
}
}
public void insertAtTail(E element) {
Node<E> newNode = new Node<E>(element, null);
if (head != null) {
tail.setNext(newNode);
} else {
head = newNode;
}
tail = newNode;
size++;
}
public static void main(String[] args) { // test
}
}
如果两个条件都不匹配,你似乎错过了去下一个节点。
public int count(E elem) {
Node <E> currentNode = new Node <E>();
currentNode = head;
int counter = 0;
for (int i = 0; i<size; i++){
if (currentNode == null) {
return 0; //current is null
}
else if (elem.equals(currentNode.getElement())){
counter++;
}
currentNode = currentNode.getNext();
}
return counter;
}
我想,史密斯先生的回答是钉在它上面的。 我不会使用大小的循环,但采取的事实是没有下一个作为底部。 当然,你的计数方法必须在所有情况下返回计数器,而不是0。
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