對自定義的物件屬性進行排序，一般是實現Comparable介面或實現Comparator介面

1. 實現Comparable介面

package CollectionKnowledge;

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

/**
 * 集合自定義屬性升序排序示例
 * @author sunlh
 *
 */
public class ComparatorSort {

    public
 
 static void main(String[] args) {
        List<UserBean> list = new ArrayList<>();
        UserBean user1 = new UserBean("2", "張三", "男", 23);
        UserBean user2 = new UserBean("4", "李四", "男", 24);
        UserBean user3 = new UserBean("3", "王五", "男", 25);
        UserBean user4 = new
 
 UserBean("1", "馬六", "男", 26);
        list.add(user1);
        list.add(user2);
        list.add(user3);
        list.add(user4);
        System.out.println("排序前資料");
        for (UserBean userBean : list)
            System.out.println(userBean.toString());
        System.out.println("排序後資料");
        // 呼叫排序方法，進行排序
 

        ComparatorSort.sortById(list);
        for (UserBean userBean : list)
            System.out.println(userBean.toString());
    }

    /**
     * 按照集合id升序排序
     * @param list
     */
    public static void sortById(List<UserBean> list) {
        Collections.sort(list, new Comparator<UserBean>() {
            @Override
            public int compare(UserBean u1, UserBean u2) {
                String id1 = u1.getId();
                String id2 = u2.getId();
                return id1.compareToIgnoreCase(id2);// 忽略大小寫進行升序排序
            }
        });
    }

}

/**
 * 使用者pojo
 * @author sunlh
 *
 */
class UserBean{
    private String id;
    private String name;
    private String sex;
    private int age;

    public UserBean(String id, String name, String sex, int age) {
        this.id = id;
        this.name = name;
        this.sex = sex;
        this.age = age;
    }

    public UserBean() {

    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "UserBean [id=" + id + ", name=" + name + ", sex=" + sex
                + ", age=" + age + "]";
    }

}

輸出結果：

排序前資料
UserBean [id=2, name=張三, sex=男, age=23]
UserBean [id=4, name=李四, sex=男, age=24]
UserBean [id=3, name=王五, sex=男, age=25]
UserBean [id=1, name=馬六, sex=男, age=26]
排序後資料
UserBean [id=1, name=馬六, sex=男, age=26]
UserBean [id=2, name=張三, sex=男, age=23]
UserBean [id=3, name=王五, sex=男, age=25]
UserBean [id=4, name=李四, sex=男, age=24]

2. 實現Comparable介面

package CollectionKnowledge;

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

public class ComparableSort {

    public static void main(String[] args) {
        List<UserBean2> list = new ArrayList<>();
        UserBean2 user1 = new UserBean2("2", "張三", "男", 23);
        UserBean2 user2 = new UserBean2("4", "李四", "男", 24);
        UserBean2 user3 = new UserBean2("3", "王五", "男", 25);
        UserBean2 user4 = new UserBean2("1", "馬六", "男", 26);
        list.add(user1);
        list.add(user2);
        list.add(user3);
        list.add(user4);
        System.out.println("排序前資料");
        for (UserBean2 userBean2 : list)
            System.out.println(userBean2.toString());
        System.out.println("排序後資料");
        Collections.sort(list);
        for (UserBean2 userBean2 : list)
            System.out.println(userBean2.toString());
    }
}

/**
 * 使用者pojo
 * @author sunlh
 *
 */
class UserBean2 implements Comparable<UserBean2>{
    private String id;
    private String name;
    private String sex;
    private int age;

    public UserBean2(String id, String name, String sex, int age) {
        this.id = id;
        this.name = name;
        this.sex = sex;
        this.age = age;
    }

    public UserBean2() {

    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "UserBean [id=" + id + ", name=" + name + ", sex=" + sex
                + ", age=" + age + "]";
    }

    @Override
    public int compareTo(UserBean2 o) {
        return this.id.compareToIgnoreCase(o.getId());
    }
}

輸出結果(同上面一樣)：

排序前資料
UserBean [id=2, name=張三, sex=男, age=23]
UserBean [id=4, name=李四, sex=男, age=24]
UserBean [id=3, name=王五, sex=男, age=25]
UserBean [id=1, name=馬六, sex=男, age=26]
排序後資料
UserBean [id=1, name=馬六, sex=男, age=26]
UserBean [id=2, name=張三, sex=男, age=23]
UserBean [id=3, name=王五, sex=男, age=25]
UserBean [id=4, name=李四, sex=男, age=24]

3. Comparable與Comparator介面的區別