ArrayList容器排序 comparator介面與comparable介面的使用__JAVA

1、實體類實現comparable介面，重寫compareTo方法

package io;import java.text.DateFormat;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Date;public class Student implements Comparable<Student>{private String name;private int age;private Date birthDay;public Student(String name, int age, String birthDay) {super();this.name = name;this.age = age;DateFormat ds=new SimpleDateFormat("yyyy-MM-dd");try {this.birthDay = ds.parse(birthDay);} catch (ParseException e) {e.printStackTrace();};}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 Date getBirthDay() {return birthDay;}public void setBirthDay(Date birthDay) {this.birthDay = birthDay;}//按名字降序 按生日升序@Overridepublic int compareTo(Student o) {int result=0;result=-this.name.compareTo(o.name);if(result==0){result=this.birthDay.compareTo(o.birthDay);}return result;}@Overridepublic String toString() {return "Student [name=" + name + ", age=" + age + ", birthDay=" + birthDay + "]";}}

package io;import java.util.ArrayList;import java.util.Collections;import java.util.List;public class App {public static void main(String[] args) {List<Student> list=new ArrayList<Student>();list.add(new Student("張三", 20, "1987-10-5"));list.add(new Student("王五", 22, "1986-10-5"));list.add(new Student("趙六", 25, "1988-10-5"));list.add(new Student("王七", 19, "1980-10-5"));Collections.sort(list);for(Student s:list){System.out.println(s);}}}

2、建立新的業務類實現comparator介面，重寫compare方法。

package io;import java.text.DateFormat;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Date;public class Student {private String name;private int age;private Date birthDay;public Student(String name, int age, String birthDay) {super();this.name = name;this.age = age;DateFormat ds=new SimpleDateFormat("yyyy-MM-dd");try {this.birthDay = ds.parse(birthDay);} catch (ParseException e) {e.printStackTrace();};}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 Date getBirthDay() {return birthDay;}public void setBirthDay(Date birthDay) {this.birthDay = birthDay;}@Overridepublic String toString() {return "Student [name=" + name + ", age=" + age + ", birthDay=" + birthDay + "]";}}

package io;import java.util.Comparator;public class BirthdayComp implements Comparator<Student>{@Overridepublic int compare(Student o1, Student o2) {return o1.getBirthDay().compareTo(o2.getBirthDay());}}

package io;import java.util.ArrayList;import java.util.Collections;import java.util.List;public class App {public static void main(String[] args) {List<Student> list=new ArrayList<Student>();list.add(new Student("張三", 20, "1987-10-5"));list.add(new Student("王五", 22, "1986-10-5"));list.add(new Student("趙六", 25, "1988-10-5"));list.add(new Student("王七", 19, "1980-10-5"));Collections.sort(list, new BirthdayComp());for(Student s:list){System.out.println(s);}}}