View difference between Paste ID: VGUC7Ra7 and hcbPEHiT

 import java.util.*;
 
 
 public class Main {
     static Map<Integer, Vertex> distances = new HashMap<>();
     static int max = 0;
     public static void main(String[] args) {
         Scanner in = new Scanner(System.in);
         int N = in.nextInt();
         List<Vertex> vertices = new ArrayList<>();
         List<Vertex> leaves = new ArrayList<>();
         for (int i = 0; i < N; i++) {
             Vertex current = new Vertex(in.nextInt());
             vertices.add(current);
             leaves.add(current);
         }
         for (int i = 0; i < N - 1; i++) {
             Vertex one = vertices.get(in.nextInt() - 1);
             Vertex two = vertices.get(in.nextInt() - 1);
             one.addLink(two);
             two.addLink(one);
             if (one.getLinks() > 1) {
                 leaves.remove(one);
             }
             if (two.getLinks() > 1) {
                 leaves.remove(two);
             }
         }
 
         dfs(leaves.get(0), null, leaves.get(0).value);
 
         Vertex start = distances.get(max);
         dfs(start, null, start.value);
         System.out.println(max);
 
     }
 
     private static void dfs(Vertex vertex, Vertex parent, int distance) {
         List<Vertex> links = vertex.links;
         for (Vertex link :
                 links) {
             if (link.equals(parent)){
                 distances.put(distance, vertex);
                 max = Math.max(max, distance);
                 continue;
             }
             dfs(link, vertex, distance + link.value);
         }
 
     }
 
     static class Vertex{
         List<Vertex> links = new ArrayList<>();
         int value;
 
         public Vertex(){
         }
         public Vertex(int value){
             setValue(value);
         }
 
         void setValue(int value){
             this.value = value;
         }
 
         void addLink(Vertex link){
             links.add(link);
         }
 
         int getLinks(){
             return links.size();
         }
     }
 }