public class Student implements Comparable<Student> { private int id; private int age; private String name; public Student(int id, int age, String name) { this.id = id; this.age = age; this.name = name; } @Override public int compareTo(Student o) { //降序 //return o.age - this.age; //升序 return this.age - o.age; } @Override public String toString() { return "Student{" + "id=" + id + ", age=" + age + ", name='" + name + '\'' + '}'; } }
返回值 | 含义 |
---|---|
负整数 | 当前对象的值 < 比较对象的值 , 位置排在前 |
零 | 当前对象的值 = 比较对象的值 , 位置不变 |
正整数 | 当前对象的值 > 比较对象的值 , 位置排在后 |
public static void main(String args[]){ List<Student> list = new ArrayList<>(); list.add(new Student(1,25,"关羽")); list.add(new Student(2,21,"张飞")); list.add(new Student(3,18,"刘备")); list.add(new Student(4,32,"袁绍")); list.add(new Student(5,36,"赵云")); list.add(new Student(6,16,"曹操")); System.out.println("排序前:"); for (Student student : list) { System.out.println(student.toString()); } //使用默认排序 Collections.sort(list); System.out.println("默认排序后:"); for (Student student : list) { System.out.println(student.toString()); } }
排序前: Student{id=1, age=25, name='关羽'} Student{id=2, age=21, name='张飞'} Student{id=3, age=18, name='刘备'} Student{id=4, age=32, name='袁绍'} Student{id=5, age=36, name='赵云'} Student{id=6, age=16, name='曹操'} 默认排序后: Student{id=6, age=16, name='曹操'} Student{id=3, age=18, name='刘备'} Student{id=2, age=21, name='张飞'} Student{id=1, age=25, name='关羽'} Student{id=4, age=32, name='袁绍'} Student{id=5, age=36, name='赵云'}
//自定义排序1 Collections.sort(list, new Comparator<Student>() { @Override public int compare(Student o1, Student o2) { return o1.getId() - o2.getId(); } });
compare(Student o1, Student o2) 方法的返回值跟 Comparable<> 接口中的 compareTo(Student o) 方法 返回值意思相同。另一种写法如下:
//自定义排序2 list.sort(new Comparator<Student>() { @Override public int compare(Student o1, Student o2) { return o1.getId() - o2.getId(); } });
排序前: Student{id=1, age=25, name='关羽'} Student{id=2, age=21, name='张飞'} Student{id=3, age=18, name='刘备'} Student{id=4, age=32, name='袁绍'} Student{id=5, age=36, name='赵云'} Student{id=6, age=16, name='曹操'} 自定义排序后: Student{id=1, age=25, name='关羽'} Student{id=2, age=21, name='张飞'} Student{id=3, age=18, name='刘备'} Student{id=4, age=32, name='袁绍'} Student{id=5, age=36, name='赵云'} Student{id=6, age=16, name='曹操'}
以上所述是小编给大家介绍的Java使用Collections.sort()排序的方法,希望对大家有所帮助。在此也非常感谢大家对网站的支持!