I'm trying to solve Farthest Nodes in a Tree (II) Problem in java . it's from lightOj.But I'm getting MLE(it takes 151552 KB memory).How to solve it using java.

my code :

import java.util.ArrayList;
import java.util.Scanner;
import java.io.IOException;
import java.io.PrintWriter;

public class FarthestNodesinaTree {

    public static void main(String args[]) throws IOException {
        Scanner scan = new Scanner(System.in);
        int t = scan.nextInt();
        int q = 1;
        PrintWriter out = new PrintWriter(System.out);

        while (t-- > 0) {
            mx = 0;
            short n = (short) scan.nextInt();
            ArrayList<Node>[] node = new ArrayList[n];
            for (int i = 0; i < n; i++) {
                node[i] = new ArrayList<Node>();
            }
            for (int i = 0; i < n - 1; i++) {
                addEdge((short) scan.nextInt(), (short) scan.nextInt(), scan.nextInt(), node);
            }
            int[] a = new int[n];
            int[] b = new int[n];

            findDiameter(a, b, node, n);

            out.println("Case " + q++ + ":");
            for (int i = 0; i < n; i++) {
                out.println(farNode(i, a, b));
            }
        }
        out.close();

    }

    static void addEdge(short u, short v, int w, ArrayList<Node>[] node) {
        {
            node[u].add(new Node(v, w));
            node[v].add(new Node(u, w));
        }
    }

    static int currNode;
    static int mx = 0;

    static void findDiameter(int[] xDis, int[] yDis, ArrayList<Node>[] node, int n) {

        findDiameterHelper(0, 0, xDis, -1, node);
        int x = currNode;

        mx = Integer.MIN_VALUE;
        findDiameterHelper(x, 0, xDis, -1, node);
        int y = currNode;
        mx = Integer.MIN_VALUE;

        findDiameterHelper(y, 0, yDis, -1, node);

    }

    static int farNode(int u, int[] xDis, int[] yDis) {
        return Math.max(xDis[u], yDis[u]);
    }

    static void findDiameterHelper(int u, int w, int[] arr, int par, ArrayList<Node>[] node) {
        if (w > mx) {
            mx = w;
            currNode = u;
        }

        arr[u] = w;
        for (Node child : node[u]) {
            if (child.v != par) {
                findDiameterHelper(child.v, child.w + w, arr, u, node);

            }
        }
    }
}

class Node {

    short v;
    int w;

    Node(short a, int b) {
        v = a;
        w = b;
    }

}