MetallicPriest :
I am learning Generics in Java. For that, I tried out a simple LinkedList like that.
class Node {
private int age;
private String name;
private Node next;
public Node(int age, String name) {
this.age = age;
this.name = name;
this.next = null;
}
public int getAge() {
return this.age;
}
public String getName() {
return this.name;
}
public Node getNext() {
return this.next;
}
public void setNext(Node next) {
this.next = next;
}
}
class LinkedList<T> {
private T head;
private T current;
public LinkedList() {
head = null;
current = null;
}
public void append(T x) {
if (head == null) {
head = x;
current = x;
}
else {
current.setNext(x);
current = x;
}
}
public T getAt(int index) {
T ptr = head;
for(int i = 0; i < index; i++) {
ptr = ptr.getNext();
}
return ptr;
}
}
class Main {
public static void main(String[] args) {
LinkedList<Node> list = new LinkedList<Node>();
list.append(new Node(39, "John"));
list.append(new Node(43, "Josh"));
Node x = list.getAt(1);
System.out.println(String.format("%d, %s", x.getAge(), x.getName()));
}
}
But I get this error, while all the methods do exist in the Node class. What mistake am I doing?
LinkedList.java:16: error: cannot find symbol
current.setNext(x);
^
symbol: method setNext(T)
location: variable current of type T
where T is a type-variable:
T extends Object declared in class LinkedList
LinkedList.java:24: error: cannot find symbol
ptr = ptr.getNext();
^
symbol: method getNext()
location: variable ptr of type T
where T is a type-variable:
T extends Object declared in class LinkedList
2 errors
Eran :
If current is of type T, you can't call methods of the Node class (such as setNext()) on current, since T can be substituted by any class when you instantiate your LinkedList.
Your Node class shouldn't be the generic type argument of LinkedList. A LinkedList should always be made of Nodes. The type of the data stored in each Node should be a generic type.
class Node<T> {
private T data;
private Node next;
public Node(T data) {
this.data = data;
this.next = null;
}
}
And the LinkedList should contain Node<T> nodes:
class LinkedList<T> {
private Node<T> head;
private Node<T> current;
}
Guess you like
Origin http://43.154.161.224:23101/article/api/json?id=327013&siteId=1