Efficient and clean Java solution:

public static long arrayManipulation(int n, List<List<Integer>> queries) {   

    Map<Integer, Long> sum = new TreeMap<>();    
    for (List<Integer> list: queries) {
        int a = list.get(0);
        int b = list.get(1);
        long k = list.get(2);
        sum.put(a, sum.getOrDefault(a, 0L) + k);
        sum.put(b + 1, sum.getOrDefault(b + 1, 0L) - k);
    }

    long max = 0L;
    long current = 0L;
    for(long value: sum.values()) {
        current += value;
        max = Math.max(max, current);
    }
    return max;
}