997. Find the Town Judge

class Solution {
    
    LinkedList<Integer> graph[];
    int vertices;
    
    public Solution(int n){
        vertices = n;
        graph = new LinkedList[n];
        for(int i =0;i<n;i++)
            graph[i] = null;
    }
    public Solution(){}
    public void addEdge(int x, int y){
        if(graph[x-1] == null){
            graph[x-1] = new LinkedList<>();
        }
        graph[x-1].add(y);
    }
    
    public int checkIfEmpty(){
        int count = 0;
        int ans = -1;
        for(int i =0;i<graph.length;i++)
        {
            if(graph[i] == null){
                count++;
                ans = i;
            }
        }
        if(count == 1)
            return ans;
        return -1;
    }
    public boolean checkTrust(int indexOfJudge){
        for(int i =0;i<graph.length;i++)
        {
            if(i == indexOfJudge)
                continue;
            Iterator it = graph[i].iterator();
            boolean flag = false;
            while(it.hasNext()){
                Integer value = (Integer)it.next();
                if(value == indexOfJudge+1){
                    flag = true;
                    break;
                }
            }
            if(!flag) // not found
                return flag;
        }
        return true;
    }
    public int findJudge(int n, int[][] trust) {
        if(n== 0)
            return -1;
        if(n==1)
            return 1;
        if(trust.length == 0)
            return -1;
        Solution solution = new Solution(n);
        for(int i =0;i<trust.length;i++){
            solution.addEdge(trust[i][0], trust[i][1]);
        }
        int indexOfJudge = solution.checkIfEmpty();
        if( indexOfJudge == -1) return -1;
        
        if(solution.checkTrust(indexOfJudge))
            return indexOfJudge+1;
        return -1;
        
    }
}