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10鱼币
本帖最后由 Twilight.. 于 2021-12-1 00:39 编辑
利用TreeSet实现Comparable、Comparator的两种排序方式(自然排序、定制排序)
如果不采用泛型的话排序就正确了,采用泛型定制排序,结果发现排序不正确,请教大神们问题到底出在哪里了呢
不采用泛型:
- package collectionexer11_5;
- import java.util.Comparator;
- import java.util.Iterator;
- import java.util.TreeSet;
- public class TreeSetTest {
- public static void main(String[] args) {
- Employee e1 = new Employee("Tom", 22, new MyDate(1999,10,11));
- Employee e2 = new Employee("Jerry", 20, new MyDate(2001,3,23));
- Employee e3 = new Employee("Rose", 27, new MyDate(1994,5,1));
- Employee e6 = new Employee("Rrose", 27, new MyDate(1927,5,1));
- Employee e4 = new Employee("Jack", 22, new MyDate(1999,10,21));
- Employee e5 = new Employee("Jim", 44, new MyDate(1977,12,6));
- //2). 创建 TreeSet 时传入 Comparator 对象,按生日日期的先后排序。
- System.out.println("\n创建 TreeSet 时传入 Comparator 对象,按生日日期的先后排序");
- Comparator com = new Comparator() {
- @Override
- public int compare(Object o1, Object o2) {
- if(o1 instanceof Employee && o2 instanceof Employee){
- Employee e1 = (Employee) o1;
- Employee e2 = (Employee) o2;
- int year1 = e1.getBirthday().getYear();
- int year2 = e2.getBirthday().getYear();
- if(year1 < year2){
- return -1;
- }else if(year1 > year2){
- return 1;
- }else{
- int month1 = e1.getBirthday().getMonth();
- int month2 = e2.getBirthday().getMonth();
- if(month1 < month2){
- return -1;
- }else if(month1 > month2){
- return 1;
- }else{
- return Integer.compare(e1.getBirthday().getDay(), e2.getBirthday().getDay());
- }
- }
- }
- throw new RuntimeException("输入的参数类型有误");
- }
- };
- TreeSet set2 = new TreeSet(com);
- set2.add(e1);
- set2.add(e2);
- set2.add(e3);
- set2.add(e4);
- set2.add(e5);
- set2.add(e6);
- Iterator iterator2 = set2.iterator();
- while(iterator2.hasNext()){
- System.out.println(iterator2.next());
- }
- }
- }
- class Employee implements Comparable{
- private String name;
- private int age;
- private MyDate birthday;
- public Employee(String name, int age, MyDate birthday) {
- this.name = name;
- this.age = age;
- this.birthday = birthday;
- }
- public Employee() {
- }
- public String getName() {
- return name;
- }
- public void setName(String name) {
- this.name = name;
- }
- public int getAge() {
- return age;
- }
- public void setAge(int age) {
- this.age = age;
- }
- public MyDate getBirthday() {
- return birthday;
- }
- public void setBirthday(MyDate birthday) {
- this.birthday = birthday;
- }
- @Override
- public String toString() {
- return "Employee{" +
- "name='" + name + '\'' +
- ", age=" + age +
- ", birthday=" + birthday +
- '}';
- }
- @Override
- public int compareTo(Object obj){
- if(obj instanceof Employee){
- Employee e = (Employee)obj;
- return this.name.compareTo(e.name);
- }
- throw new RuntimeException("输入的数据类型不一致");
- }
- }
- class MyDate{
- private int year;
- private int month;
- private int day;
- public MyDate() {
- }
- public MyDate(int year, int month, int day) {
- this.year = year;
- this.month = month;
- this.day = day;
- }
- public int getYear() {
- return year;
- }
- public void setYear(int year) {
- this.year = year;
- }
- public int getMonth() {
- return month;
- }
- public void setMonth(int month) {
- this.month = month;
- }
- public int getDay() {
- return day;
- }
- public void setDay(int day) {
- this.day = day;
- }
- @Override
- public String toString() {
- return "MyDate{" +
- "year=" + year +
- ", month=" + month +
- ", day=" + day +
- '}';
- }
- }
复制代码
采用泛型后:
- package genericdemo12_2;
- import org.junit.Test;
- import java.util.Comparator;
- import java.util.Iterator;
- import java.util.TreeSet;
- public class EmployeeTest {
- //定制排序
- @Test
- public void testComparator(){
- Comparator<Employee> com = new Comparator<Employee>() {
- @Override
- public int compare(Employee e1, Employee e2) {
- // int year1 = e1.getBirthday().getYear();
- // int year2 = e2.getBirthday().getYear();
- // if (year1 < year2) {
- // return -1;
- // } else if (year1 > year2) {
- // return 1;
- // } else {
- // int month1 = e1.getBirthday().getMonth();
- // int month2 = e2.getBirthday().getMonth();
- // if (month1 < month2) {
- // return -1;
- // } else if (month1 > month2) {
- // return 1;
- // } else {
- // return Integer.compare(e1.getBirthday().getDay(), e2.getBirthday().getDay());
- // }
- // }
- return e1.compareTo(e2);
- }
- };
- TreeSet<Employee> set = new TreeSet<>(com);
- Employee e1 = new Employee("Tom", 22, new MyDate(1999, 10, 11));
- Employee e2 = new Employee("Jerry", 20, new MyDate(2001, 3, 23));
- Employee e3 = new Employee("Rose", 27, new MyDate(1997, 3, 12));
- Employee e6 = new Employee("RRose", 27, new MyDate(1927, 3, 12));
- Employee e4 = new Employee("Jack", 22, new MyDate(1999, 10, 21));
- Employee e5 = new Employee("Jim", 44, new MyDate(1977, 12, 6));
- set.add(e1);
- set.add(e2);
- set.add(e3);
- set.add(e4);
- set.add(e5);
- set.add(e6);
- Iterator<Employee> iterator = set.iterator();
- while(iterator.hasNext()) {
- Employee e = iterator.next();
- System.out.println(e);
- }
- }
- }
复制代码
附employee和MyDate:
- package genericdemo12_2;
- /**
- * @author whoo
- * @create 2021-11-30 10:34
- */
- public class Employee implements Comparable<Employee>{
- private String name;
- private int age;
- private MyDate birthday;
- public Employee(String name, int age, MyDate birthday) {
- this.name = name;
- this.age = age;
- this.birthday = birthday;
- }
- public Employee() {
- }
- public String getName() {
- return name;
- }
- public void setName(String name) {
- this.name = name;
- }
- public int getAge() {
- return age;
- }
- public void setAge(int age) {
- this.age = age;
- }
- public MyDate getBirthday() {
- return birthday;
- }
- public void setBirthday(MyDate birthday) {
- this.birthday = birthday;
- }
- @Override
- public String toString() {
- return "Employee{" +
- "name='" + name + '\'' +
- ", age=" + age +
- ", birihday=" + birthday +
- '}';
- }
- @Override
- public int compareTo(Employee o) {
- return this.name.compareTo(o.name);
- }
- }
复制代码- package genericdemo12_2;
- /**
- * @author whoo
- * @create 2021-11-30 10:35
- */
- public class MyDate implements Comparable<MyDate>{
- private int month;
- private int day;
- private int year;
- public MyDate(int month, int day, int year) {
- this.month = month;
- this.day = day;
- this.year = year;
- }
- public MyDate() {
- }
- public int getMonth() {
- return month;
- }
- public void setMonth(int month) {
- this.month = month;
- }
- public int getDay() {
- return day;
- }
- public void setDay(int day) {
- this.day = day;
- }
- public int getYear() {
- return year;
- }
- public void setYear(int year) {
- this.year = year;
- }
- @Override
- public String toString() {
- return "{month=" + month +
- ", day=" + day +
- ", year=" + year + "}";
- }
- @Override
- public int compareTo(MyDate o) {
- if(this.year < o.year){
- return -1;
- }else if(this.year > o.year){
- return 1;
- }else{
- if(this.month < o.month){
- return -1;
- }else if(this.month > o.month){
- return 1;
- }else{
- return Integer.compare(this.day, o.day);
- }
- }
- }
- }
复制代码
没问题啊,是不是你在MyDate的构造函数里写反了:
- public MyDate(int month, int day, int year)
复制代码
应改成 - public MyDate(int year, int month, int day)
复制代码
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最佳答案
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没问题啊,是不是你在MyDate的构造函数里写反了:
应改成
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