Java基礎集錦——利用Collections.sort方法對list排序

　　要想對List進行排序，可讓實體對象實現Comparable接口，重寫compareTo方法便可實現按某一屬性排序，可是這種寫法很單一，只能按照固定的一個屬性排序，沒變法變化。經過下面這種方法，能夠動態的指定List按照某一個屬性進行排序，例子很簡單，看代碼就明白了。

　　

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


public class testCollection {

    /**
     * @param args
     */
    public static void main(String[] args) {
        User u1=new User();
        u1.setName("Jessica");
        u1.setAge(20);
        User u2=new User();
        u2.setName("Abobo");
        u2.setAge(30);
        List<User> userList=new ArrayList<User>();
        userList.add(u1);
        userList.add(u2);
        MyComparator sort=new MyComparator();
        MyComparator2 sort2=new MyComparator2();
        MyComparator3 sort3=new MyComparator3();
        MyComparator4 sort4=new MyComparator4();
        Collections.sort(userList,sort);
        for (User u:userList) {
            System.out.println(u.toString()+";I am "+(userList.indexOf(u)+1)+" and I'm ordered by Name desc");
        }
        Collections.sort(userList,sort2);
        for (User u:userList) {
            System.out.println(u.toString()+";I am "+(userList.indexOf(u)+1)+" and I'm ordered by Name asc");
        }
        Collections.sort(userList,sort3);
        for (User u:userList) {
            System.out.println(u.toString()+";I am "+(userList.indexOf(u)+1)+" and I'm ordered by Age desc");
        }
        Collections.sort(userList,sort4);
        for (User u:userList) {
            System.out.println(u.toString()+";I am "+(userList.indexOf(u)+1)+" and I'm ordered by Age asc");
        }

    }
    public static class MyComparator implements Comparator<User>{
        @Override
        public int compare(User o1, User o2) {
            return -o1.getName().compareTo(o2.getName());
        }        
    }
    public static class MyComparator2 implements Comparator<User>{
        @Override
        public int compare(User o1, User o2) {
            return o1.getName().compareTo(o2.getName());
        }        
    }
    public static class MyComparator3 implements Comparator<User>{
        @Override
        public int compare(User o1, User o2) {
            return -o1.getAge().compareTo(o2.getAge());
        }        
    }
    public static class MyComparator4 implements Comparator<User>{
        @Override
        public int compare(User o1, User o2) {
            return o1.getAge().compareTo(o2.getAge());
        }        
    }
}

 結果：

Hello!My Name is Jessica and I'm 20;I am 1 and I'm ordered by Name desc
Hello!My Name is Abobo and I'm 30;I am 2 and I'm ordered by Name desc
Hello!My Name is Abobo and I'm 30;I am 1 and I'm ordered by Name asc
Hello!My Name is Jessica and I'm 20;I am 2 and I'm ordered by Name asc
Hello!My Name is Abobo and I'm 30;I am 1 and I'm ordered by Age desc
Hello!My Name is Jessica and I'm 20;I am 2 and I'm ordered by Age desc
Hello!My Name is Jessica and I'm 20;I am 1 and I'm ordered by Age asc
Hello!My Name is Abobo and I'm 30;I am 2 and I'm ordered by Age asc

 　　經過這種方法，能夠選擇爲List排序的方式了，打好地基，才能逐漸穩固的長城。