有两个对象a和b，两个集合，他们中储存了，很多条学生的信息，但是a和b中的学生信息由重复的（比如sno 相同），现在要求通过contains（）方法，来把a和b合并为一个list对象，并且，要去掉重复的学生信息，并且在list中存储的学生信息要按照学号升序存储。

Student.java

package test;
 
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.List;
 
public class Student{
    String sno;
    String sname;
 
    public Student (String sno, String sname){
        this.sno = sno;
        this.sname = sname;
    }
 
    public String getSno (){
        return sno;
    }
 
    public void setSno (String sno){
        this.sno = sno;
    }
 
    public String getSname (){
        return sname;
    }
 
    public void setSname (String sname){
        this.sname = sname;
    }
 
    @Override
    public String toString (){
        StringBuilder builder = new StringBuilder ();
        builder.append ("Student [sno=").append (sno).append (", sname=").append (sname).append ("]");
        return builder.toString ();
    }
 
    private static List<Student> contains ( List<Student> a, List<Student> b ){
        List<Student> list = new LinkedList<Student>();
        list.addAll (a);
        String temp = list.toString ();
        for (Student student : b){
            String reg = "sno=" + student.getSno () + ",";
            if (temp.indexOf (reg) == -1){
                list.add (student);
            }
        }
        Collections.sort (list, new Comparator<Student> (){
            @Override
            public int compare (Student o1, Student o2){
                int a = Integer.parseInt (o1.getSno ());
                int b = Integer.parseInt (o2.getSno ());
                if (a > b){
                    return 1;
                } else if (a < b){
                    return -1;
                } else {
                    return 0;
                }
            }
        });
        return list;
    }
 
    public static void main ( String[] args ){
        Student s1 = new Student ("100", "ko");
        Student s2 = new Student ("102", "pi");
        Student s3 = new Student ("101", "pid");
        Student s4 = new Student ("102", "pi");
        List<Student> a = Arrays.asList (s1, s2);
        List<Student> b = Arrays.asList (s3, s4);
        List<Student> c = contains (a, b);
        for ( Student student : c ){
            System.out.println (student);
        }
    }
}