Java – how to find the maximum value in a binary tree

I have to complete the method maxelem (node) in this way, and the method maxelem () returns the maximum value contained in the binary tree

How can I do this? I don't know how to do it

public class BinaryTree {

    protected class Node {
        protected Integer element;
        protected Node left;
        protected Node right;

        Node(int element) {
            this.element = element;
            left = right = null;
        }

        Node(int element,Node left,Node right) {
            this.element = element;
            this.left = left;
            this.right = right;
        }

    } //end Node class

    public class NodeReference {
        private Node node;

        private NodeReference(Node node) {
            this.node = node;
        }

        public int getElement() {
            return node.element;
        }

        public void setElement(int e) {
            node.element = e;
        }
    }

    protected Node root;

    public BinaryTree() {
        root = null;
    }

    private class BoolNode {

        boolean found; 
        Node node;

        BoolNode(boolean found,Node node) {
            this.found = found;
            this.node = node;
        }
    }

    public int maxElem() {
        if(root == null) 
            throw new IllegalStateException("Empty tree.");
        return maxElem(root);
    }


    private static int max3(int x,int y,int z) {
        return max(x,max(y,z));
    }

    private int maxElem(Node node) {
        //...
    }

}

Thank you.

Solution

Try:

private int maxElem(Node node) {
    int max = node.element;
    if(node.left != null) {
        max = Math.max(max,maxElem(node.left));
    }
    if(node.right != null) {
        max = Math.max(max,maxElem(node.right));
    }
    return max;
}