Sort arraylist of arrays based on two prioritized elements

Question

I have an ArrayList of arrays, which I want to sort based on the arrays' two integers. I want to sort them based on a primary integer in descending order, then sort them based on one another secondary integer existing in arrays in ascending order, while maintaining the first order.

Say I have an array1 with [1, 3]; array2 with [1, 1]; array3 with [0, 50].

At first, they are unsorted in the ArrayList array1, array2 and array3. After sorting they are in order as follows: array2, array1, and array3.

Answer 1

you can sort the list by Collections.sort .

public void sort(List<Integer[]> list)
     return Collections.sort(list, (o1, o2) -> o1[0].equals(o2[0]) ? o1[1] - o2[1] : o1[0] - o2[0]);
}

we use Lambda expression to compare to Integer[]

when you want to sort two Integer (A,B) descendingly, you must compare them like BA and if you want to sort ascendingly, you should use AB

Answer 2

一个带有 java8 的单行

list.stream().sorted((prim, sec) -> prim[0] == sec[0] ? prim[1] - sec[1] : prim[0] - sec[0]).collect(Collectors.toList());