请问为什么加上 - 减号，就能从大到小进行排序？

Question

class test {
        @Test
        public void testThree() {
            String[] arr = new String[]{"AA", "CC", "DD", "GG", "JJ", "ZZ", "BB"};
            Arrays.sort(arr, new Comparator() {
                @Override
                public int compare(Object o1, Object o2) {
                    if (o1 instanceof String && o2 instanceof String) {
                        String str1 = (String) o1;
                        String str2 = (String) o2;
                        System.out.println(str1.compareTo(str2));

                        return -str1.compareTo(str2);
                    }
                    throw new RuntimeException("传入的数据类型不一致！");
                }
            });
        }
    }

Answer 1

str1.compareTo(str2); 返回的值是 0、1、-1。加个减号取反