Java List 排序

 

1. 调用java.util.Collections.sort(List list)方法进行排序 

   List内的Object都必须实现了Comparable接口 

public class Account implements Comparable {
    private String name;
    private String accessLevel;
    public Account(String name,String accessLevel) {
        this.name = name;
        this.accessLevel = accessLevel;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setAccessLevel(String accessLevel) {
        this.accessLevel = accessLevel;
    }

    public String getAccessLevel() {
        return accessLevel;
    }

    public int compareTo(Object o) {
        Account account = (Account)o;
        return this.getName().compareTo(account.getName());
    }
}

 

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class TestAccount {
    public static void main(String[] args) {
        List<Account> accountList = new ArrayList<Account>();
        accountList.add(new Account("abc","12"));
        accountList.add(new Account("qbc","12"));
        accountList.add(new Account("fbc","11"));
        accountList.add(new Account("gbc","11"));
        accountList.add(new Account("wbc","15"));
        Collections.sort(accountList);
        for(Account account:accountList){
            System.out.println(account.getName()+" "+account.getAccessLevel());
            System.out.println("-------");
        }
    }
}

 

2. 调用 java.util.Collections.sort(List list，Comparator c)

public class Person { 
    private String name;
    private String age;
    public Person(String name,String age) {
        this.name = name;
        this.age = age;
    }

    public void setName(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }

    public void setAge(String age) {
        this.age = age;
    }
    public String getAge() {
        return age;
    }
}

声明一个PersonComparator类 

import java.util.Comparator;

public class PersonComparator implements Comparator {
    public PersonComparator() {
        super();
    }

    public int compare(Object o1, Object o2) {
        Person person1 = (Person)o1;
        Person person2 = (Person)o2;
        int compareTo = person1.getName().compareTo(person2.getName());
        if(compareTo == 0){
            compareTo = person1.getAge().compareTo(person2.getAge());
        }
        return compareTo;
    }
}

 

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class TestPerson {
    public static void main(String[] args) {
        List<Person> personList = new ArrayList<Person>();
        personList.add(new Person("abc","32"));
        personList.add(new Person("abc","12"));
        personList.add(new Person("fbc","22"));
        personList.add(new Person("gbc","52"));
        personList.add(new Person("wbc","12"));
        PersonComparator personComp = new PersonComparator();
        Collections.sort(personList,personComp);
        for(Person person:personList){
            System.out.println(person.getName()+" "+person.getAge());
            System.out.println("-------");
        }
    }
} 

  临时声明一个Comparator 来实现排序

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class TestPerson {
    public static void main(String[] args) {
        List<Person> personList = new ArrayList<Person>();
        personList.add(new Person("abc","32"));
        personList.add(new Person("abc","12"));
        personList.add(new Person("fbc","22"));
        personList.add(new Person("gbc","52"));
        personList.add(new Person("wbc","12"));
        Collections.sort(personList,new Comparator<Person>(){           
                public int compare(Person o1, Person o2) {
                    Person person1 = (Person)o1;
                    Person person2 = (Person)o2;
                    int compareTo = person1.getName().compareTo(person2.getName());
                    if(compareTo == 0){
                        compareTo = person1.getAge().compareTo(person2.getAge());
                    }
                    return compareTo;
                }
            });
        
//        PersonComparator personComp = new PersonComparator();
//        Collections.sort(personList,personComp);
        for(Person person:personList){
            System.out.println(person.getName()+" "+person.getAge());
            System.out.println("-------");
        }
    }
}