java中对List接口的实例按实体的字段排序。如下例：

package se;

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

class Employee {
    private int level;
    private int salary;
    private int years;

    public int getLevel() {
        return level;
    }

    public void setLevel(int level) {
        this.level = level;
    }

    public int getSalary() {
        return salary;
    }

    public void setSalary(int salary) {
        this.salary = salary;
    }

    public int getYears() {
        return years;
    }

    public void setYears(int years) {
        this.years = years;
    }

    @Override
    public String toString() {
        return "Employee [level=" + level + ", salary=" + salary + ", years="
                + years + "]";
    }

}

public class CollectionsListSortTest {

    // 按级别工资入职年数递减排序
    public static void main(String[] args) {
        List<Employee> list = new ArrayList<Employee>();

        Employee e = new Employee();
        e.setLevel(1);
        e.setSalary(300);
        e.setYears(4);
        list.add(e);

        e = new Employee();
        e.setLevel(1);
        e.setSalary(500);
        e.setYears(4);
        list.add(e);

        e = new Employee();
        e.setLevel(2);
        e.setSalary(500);
        e.setYears(4);
        list.add(e);

        e = new Employee();
        e.setLevel(1);
        e.setSalary(300);
        e.setYears(5);
        list.add(e);
        Collections.sort(list, new Comparator<Employee>() {
            public int compare(Employee e1, Employee e2) {
                int a = e1.getLevel() - e2.getLevel();
                if (a != 0) {
                    return a > 0 ? -1 : 1;
                }
                a = e1.getSalary() - e2.getSalary();
                if (a != 0) {
                    return a > 0 ? -1 : 1;
                }
                a = e1.getYears() - e2.getYears();
                return a > 0 ? -1 : 1;
            }
        });

        for (Employee em : list) {
            System.out.println(em);
        }
    }

}