B+ Tree help ! ! !

import java.util.*;
public class Tree {
    
    private int p;
    private int pLeaf;
    private float fillFactor;
    Node root;
    public Tree(int p, int pLeaf, float fillFactor) {
        this.p = p;
        this.pLeaf = pLeaf;
        this.fillFactor = fillFactor;
        this.root = new NodeLeaf(pLeaf);        
    }
    
    public void insert(int key){
        Node n;
        Stack parents = new Stack();
        int numberOfPointers;
        n = this.root;
        while ( !(n instanceof NodeLeaf) ){
            parents.push(n);
            numberOfPointers = this.p;
            if (key <= n.printKey(0)) {
                n = n.children[0];
            }
            else if ( key > n.printKey(numberOfPointers - 1) && n.printKey(numberOfPointers - 1) != 0 ){
                n = n.children[numberOfPointers];
            }
            else{
                int position;
                // It searches the Node for the position where the key must be placed.
                position = n.search(key);
                n = n.printChildren(position);
            }
        }
        
        // It searches the NodeLeaf if the key already exists in the database.
        int found;
        found = n.search(key);
        if (found == 1){
            System.out.println (" The record is already in the databse. It cannot be inserted again!");
        }
        else{
            if ( !(n.isTheNodeFull()) ){
                n.insert(key);
            }
            else{
                NodeLeaf temp = new NodeLeaf(pLeaf + 1);
                temp = n;
                temp.insert(key);
                NodeLeaf newLeaf = new NodeLeaf(pLeaf); 
                newLeaf.pNext = n.pNext;
            }
        }
    }

    
    public void delete(){
    }
    
    public void update(){
    }
    
    public void search(){
    }
    
}

public class Node {
    private int p;
    private int []key;
    NodeLeaf []children;
    
    public Node() {
    }
    
    
    public Node(int p) {
        this.p = p;
        this.key = new int[p-1];
        this.children = new NodeLeaf[p];
    }
    
    public void insert(int key){
    }
    
    public void delete(){
    }
    
    public void update(){
    }
    
    /* The function search, searches between witch keys fits the gives search key. */
    /* When the position i in the arreay is found, it is returned.                 */
    public int search(int key){
        int i;
        for(i=1; i<this.key.length-1; i++){
            if (  ( this.key[i-1]< key ) && ( key <= this.key[i] )  ){
                break;
            }
        }
        return i;
    }
    
    public boolean isTheNodeFull(){
        for (int i=0; i<this.key.length; i++) {
            if ( this.key[i] == 0 ){
                return false;
            }
        }
        return true;
    }
        
    
    public Node printChildren(int i){
        return this.children[i];
    }
    
    public int printKey(int i){
        return this.key[i];
    }
    
    public void changeChildren(int i, NodeLeaf newChildren){
        this.children[i] = newChildren;
    }
    
    public void changeKey(int i, int newKey){
        this.key[i] = newKey;
    }
    
}

public class NodeLeaf extends Node{
    private int pLeaf;
    int []key;
    NodeLeaf pNext;
    
    public NodeLeaf() {
    }
    
    
    public NodeLeaf(int pLeaf) {
        this.pLeaf = pLeaf;
        this.key = new int[pLeaf];
    }
    
    public void insert(int key){
        for(int i=0; i<this.key.length; i++){
            if (this.key[i] == 0){
                this.key[i] = key;
            }
        }
    }
    
    public void delete(){
    }
    
    public void update(){
    }
    
    
    /* The search function search for the key in the NodeLeaf.        */
    /* If found, it means that the key already exists in the database */
    /* so it prints the apropriate message and returns 0. If not found*/
    /* thesn returns 1.                                               */
    public int search(int key){
        int i;
        for (i=0; i<this.key.length; i++) {
            if ( this.key[i] == key ){
                System.out.println("The record is in tha database");
                return 1;
            }
        }
        return 0;
    }
    
    public boolean isTheNodeFull(){
        for (int i=0; i<this.key.length; i++) {
            if ( this.key[i] == 0 ){
                return false;
            }
        }
        return true;
    }
    
    
}

Tree.java [49:1] incompatible types
found   : Node
required: NodeLeaf
                temp = n;
                       ^
Tree.java [52:1] cannot resolve symbol
symbol  : variable pNext 
location: class Node
                newLeaf.pNext = n.pNext;
                                 ^
2 errors
Errors compiling Tree.