Java常用方法

• 数组拷贝

    int[] from = [1,2,3];
    int[] to = new int[a.length];
    System.arraycopy(from, 0, to, 0, length);
    Arrays.fill(from, 100);

• 排序

int[] nums = new int[]{1,2,3,1};
List<Integer> a= Arrays.stream(nums).boxed().collect(Collectors.toList());
System.out.println(a);
System.out.println(Arrays.toString(nums));

a.sort(new Comparator<Integer>() {
    public int compare(Integer a, Integer t){
        return a - t;
    }
});

a.sort(Comparator.naturalOrder());
Collections.sort(a);
Collections.sort(a, Comparator.naturalOrder());

int[] nums = new int[]{1,2,3,1};
Arrays.sort(nums);