java的list集合如何根据对象中的某个字段排序？

转自：http://blog.csdn.net/wangjuan_01/article/details/51351633

 

List集合按某个字段排序

package wjtest_01;

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

public class ListSort<E> {
    @SuppressWarnings("unchecked")
    public static void main(String[] args) {

        List<Student> list = new ArrayList<Student>();

        // 创建3个学生对象，年龄分别是20、19、21，并将他们依次放入List中
        Student s1 = new Student();
        s1.setAge(20);
        s1.setUsable(true);
        Student s2 = new Student();
        s2.setAge(19);
        s2.setUsable(true);
        Student s3 = new Student();
        s3.setAge(21);
        s3.setUsable(false);
        list.add(s1);
        list.add(s2);
        list.add(s3);

        System.out.println("排序前：" + list);
        Collections.sort(list, new Comparator<Student>() {

            @Override
            public int compare(Student o1, Student o2) {
                // 按照学生的年龄进行升序排列
                if (o1.getAge() > o2.getAge()) {
                    return 1;
                }
                if (o1.getAge() == o2.getAge()) {
                    return 0;
                }
                return -1;
            }
        });

        System.out.println("升序排序后：" + list);

        Collections.sort(list, new Comparator<Student>() {

            public int compare(Student o1, Student o2) {

                // 按照学生的年龄进行降序排列
                if (o1.getAge() > o2.getAge()) {
                    return -1;
                }
                if (o1.getAge() == o2.getAge()) {
                    return 0;
                }
                return 1;
            }
        });

        System.out.println("降序排序后：" + list);

        Boolean b1 = true; // 创建Boolean对象1

        Boolean b2 = false; // 创建Boolean对象0

        Boolean b3 = true; // 创建Boolean对象1
        System.out.println(b1);

        int i;

        i = b1.compareTo(b2); // b1和b2进行比较

        System.out.println(i);//1-0

        i = b2.compareTo(b1); // b2和b1进行比较

        System.out.println(i);//0-1

        i = b1.compareTo(b3); // b1和b3进行比较

        System.out.println(i);//1-1
    }
}

class Student{

    private int age;

    private Boolean isUsable;

    public int getAge() {
        return age;
    }

    public Boolean isUsable() {
        return isUsable;
    }

    public void setUsable(Boolean isUsable) {
        this.isUsable = isUsable;
    }

    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return getAge()+"";
    }
}