我正在尝试使用add方法将元素添加到LinkedList。这就是代码的样子:
/**
* A singly linked list.
*
* @author
* @version
*/
public class LinkedList<T> {
private ListElement<T> first; // First element in list.
private ListElement<T> last; // Last element in list.
public LinkedList<T> asd;
private int size; // Number of elements in list.
/**
* A list element.
*/
private static class ListElement<T> {
public T data;
public ListElement<T> next;
public ListElement(T data) {
this.data = data;
this.next = null;
}
}
/**
* This TEST METHOD returns true if the following invariants hold:
* <ul>
* <li> size equals the number of list elements, </li>
* <li> if size == 0, first == null and last == null, </li>
* <li> if size > 0, first != null and last != null, </li>
* <li> if size == 1, first == last, </li>
* <li> last.next == null. </li>
* </ul>
*/
public boolean isHealthy() {
return false;
}
/**
* Creates an empty list.
*/
public LinkedList() {
asd = new LinkedList<T>();
}
/**
* Inserts the given element at the beginning of this list.
*/
public void addFirst(T element) {
asd.add(element);
}
/**
* Inserts the given element at the end of this list.
*/
public void addLast(T element) {
}
/**
* Returns the first element of this list.
* Returns <code>null</code> if the list is empty.
*/
public T getFirst() {
// TODO
return null;
}
/**
* Returns the last element of this list.
* Returns <code>null</code> if the list is empty.
*/
public T getLast() {
return null;
}
/**
* Returns the element at the specified position in this list.
* Returns <code>null</code> if <code>index</code> is out of bounds.
*/
public T get(int index) {
return null;
}
/**
* Removes and returns the first element from this list.
* Returns <code>null</code> if the list is empty.
*/
public T removeFirst() {
return null;
}
/**
* Removes all of the elements from this list.
*/
public void clear() {
}
/**
* Returns the number of elements in this list.
*/
public int size() {
return 0;
}
/**
* Returns <code>true</code> if this list contains no elements.
*/
public boolean isEmpty() {
return false;
}
/**
* Returns a string representation of this list. The string
* representation consists of a list of the elements enclosed in
* square brackets ("[]"). Adjacent elements are separated by the
* characters ", " (comma and space). Elements are converted to
* strings by the method toString() inherited from Object.
*/
public String toString() {
return null;
}
}
问题是,当我尝试编译时,它会生成一个“找不到符号 - 方法添加(T)”错误消息。我不明白为什么它不起作用,但我是Java的新手,所以我想要一些帮助。
答案 0 :(得分:0)
是的,LinkedList 有 add
方法,但问题是您没有导入 java.util.LinkedList
。您正在实现自己的 LinkedList。因此,要么为您的类实现 add 方法,要么无需实现即可轻松使用 import java.util.LinkedList
。