import java.util.ArrayList;
import java.util.List;
class Solution {
    public boolean canFinish(int numTasks, int[][] prerequisites) {
        List<Integer>[] adjacencyList = new ArrayList[numTasks];
        int[] prereqCount = new int[numTasks];
        for (int i = 0; i < prerequisites.length; i++) {
            if(adjacencyList[prerequisites[i][1]] == null) {
                adjacencyList[prerequisites[i][1]] = new ArrayList<>();
            }
            adjacencyList[prerequisites[i][1]].add(prerequisites[i][0]);
            prereqCount[prerequisites[i][0]]++;
        }
        ...
    }
}