1. 数组排序
Arrrays.sort(list) 默认升序排序
Arrays.sort(list, comparator)默认按照comparator中实现的排序定义进行排序,以下面一个例子为例,则是按照test数组的中每一个元素的第二位进行排序,也即是按照6, 2, 4进行排序
int [][] test = new int[][]{{5, 6, 1}, {1, 2, 2}, {3, 4, 3}};
Arrays.sort(test, Comparator.comparingInt(a -> a[1]));
2. List排序
Collections.sort(list) 使用此方法要求list中存放的对象类实现Comparable接口
Collection.sort(list, comparator) 按照comparator中自定义的排序规则进行排序, 以下面这个例子为例,实现Student类对象先按照id从小到大进行排序,如果id一样,则按照name的字典序进行排序, 样例代码输出为
id:1,name:test1 id:1,name:test2 id:2,name:test id:2,name:test2 id:3,name:test1 id:4,name:test1 id:5,name:test3
Comparator<Student> stuComparator = new Comparator<Student>() {
@Override
public int compare(Student o1, Student o2) {
if (o1.id == o2.id) {
return o1.name.compareTo(o2.name);
}
return o1.id - o2.id;
}
};
List<Student> stuList = new ArrayList<>();
stuList.add(new Student(1, "test2"));
stuList.add(new Student(1, "test1"));
stuList.add(new Student(2, "test2"));
stuList.add(new Student(2, "test"));
stuList.add(new Student(3, "test1"));
stuList.add(new Student(4, "test1"));
stuList.add(new Student(5, "test3"));
Collections.sort(stuList, stuComparator);
for (Student stu: stuList) {
System.out.println(stu.toString());
}
class Student implements Comparable {
int id;
String name;
Student(int id, String name) {
this.id = id;
this.name = name;
}
public String toString() {
return "id:" +id +"," +"name:"+name;
}
@Override
public int compareTo(Object o) {
return 0;
}
}
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