i have a private Node class with a getValue() method that returns the Node's value which is of generic type. In another class i've tried doing this:

T tempItem = null; ----also generic
tempItem = currentNode.getValue();

I get a complier error unless I cast it like this: tempItem = (T) currentNode.getValue();
Honestly i don't understand why i need to do this or if it actually works or not. Can someone explain?

Edited by plasticfood

6 Years
Discussion Span
Last Post by plasticfood

What is getValue() defined to return?

Can you post a small complete program that generates the compiler error?

public class Node<T>{
    private Node <T> n;
    private T value;

    public Node(Node <T> x, T item){
        n = x;
        value = item;

    public T getValue(){
        return value;

Then in another class inside another method I wrote:
K tempItem = null;
tempItem = (K) currentNode.getValue();

Without the (K), it gives a complier error.

Edited by plasticfood


When you created the instances of Node that currentNode refers to, what did you have in the <>
How is curentNode defined?

Edited by JamesCherrill


private Node<K> currentNode = null;

if i write: tempItem = currentNode.getValue();
it generates incompatible types error.


Please post a COMPLETE program that shows the error message when you try to compile it.
Bits and pieces of code don't compile.

public class BinarySearchTree<T extends Comparable<? super T>> implements SearchTree<T> {

    private Node<T> root = null;
    private int size = 0;
    List<T> al = new ArrayList<T>();

public T getMax() {
        // TODO Auto-generated method stub
        Node tempNode = root.getRight();

        if(root == null){
            return null;
        if(root.getRight() == null){//root is largest
            return (T) root.getValue();
        else{//look in right subtree
            while(tempNode.getRight() != null){
                tempNode = tempNode.getRight();
            return tempNode.getValue();//generates error


public class Node<K> {
        private K value;
        private Node<K> left;
        private Node<K> right;

        public Node(K value) {
            this(value, null, null);

        public Node(K value, Node<K> left, Node<K> right) {
            this.value = key;
            this.left = left;
            this.right = right;

        public K getValue() {
            return value;

The rest of the code is long, but i think these are the relevant parts.

Edited by plasticfood


The posted code generates 10 errors when I try to compile it. Is that what you get?

One thing I notice is missing import statements, missing class definitions and missing methods.

Can you fix the code so it only generates the error you are asking about.

Edited by NormR1


ok nevermind i figured out what was wrong. i forgot to put <T> when i created a new tempNode.

Node<T>tempNode = root;

No longer need to cast on tempNode.getValue()

thanks everyone.

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