Couldn't insert values in BinaryTree

class bTree {
public class Node {
Node left;
Node right;
int val;
Node () {}
Node (int val){
this.val=val;
}
}
Node root;
public void insert(int val){
if (root == null){
root = new Node(val);
} else {
Node current = root;
// If val less than parent node's val go left
if (val <= root.val){
if (root.left == null){
root.left = new Node(val);
} else {
insert(val);
}
}
// If val greater than parent node's val go right
else {
if (root.right == null){
root.right = new Node(val);
} else {
insert(val);
}
}              // inner else ends
}           // outer else ends
}     // insert() ends
public void displayTree(Node root){
if (root.left != null){
displayTree(root.left);
}
System.out.print(root.val + " - ");	
if (root.right != null){
displayTree(root.right);
}
}
public static void main(String[] args) {
bTree bt = new bTree();
bt.insert(10);
bt.insert(30);
bt.insert(4);
bt.insert(5);
bt.displayTree(bt.root);
}
}

I was trying to implement a binary search tree and came across a problem inserting values in it. I have implemented it before making a Node main class but now nesting a Node class inside of a main class (like a LinkedList) is complicating it.

    public void insert(int val){
if (root == null){
root = new Node(val);
} else {
Node current = root;

Here in this bit current is always getting value of root which causes not more than 3 items to be inserted. I am aware of this problem but couldn't get around it. Any redesign in the code would be greatly appreciated.

In your code you are not passing the reference of Node in insert() method to trace down at which node position you are in the current tree.

Currently you are able to insert only 3 items because for 3 items no recursion of insert(val) is getting used, but after 3 items you are using recursion of insert call and since in that you are not passing current node position this issue is coming.

Here is the working example of insertion in binary tree :

class bTree {
Node root;
public class Node {
Node left;
Node right;
int val;
Node () {}
Node (int val){
this.val=val;
}
}
public void insert(Node currnode, int val){
if(currnode == null) {
root = new Node(val);
return;
} 
if(val <= currnode.val) {
if(currnode.left == null) {
currnode.left = new Node(val);
} else {
insert(currnode.left, val);
}
} else {
if(currnode.right == null) {
currnode.right = new Node(val);
} else {
insert(currnode.right, val);
}
}
}
public void displayTree(Node root){
if (root.left != null){
displayTree(root.left);
}
System.out.print(root.val + " - "); 
if (root.right != null){
displayTree(root.right);
}
}
public static void main(String[] args) {
bTree bt = new bTree();
bt.insert(bt.root,10);
bt.insert(bt.root,30);
bt.insert(bt.root,4);
bt.insert(bt.root,5);
bt.displayTree(bt.root);
}
}