Java作业：HashMap，ArrayList，LinkedList的使用

1.在上机练习4第1题的基础上，分别使用ArrayList、LinkedList、HashMap和TreeSet保存学生的信息，测试不同数据结构执行以下操作需要的时间：
(1)添加10,000个学生。
(2)查找100个学生。
(3)删除100个学生。
程序文件命名为Exe6_1.java。（可适当调整学生数量，以适应你自己的机器）

import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map.Entry;
import java.util.Scanner;

import javax.swing.text.html.HTMLDocument.Iterator;

public class Exe6_1 {
	int index=0;
	
	Scanner in = new Scanner(System.in);
	
	HashMap HashNo=new HashMap();
	HashMap HashName=new HashMap();
	HashMap HashAge=new HashMap();
	HashMap HashGender=new HashMap();
	
	ArrayList ListNo = new ArrayList();
	ArrayList ListName = new ArrayList();
	ArrayList ListAge = new ArrayList();
	ArrayList ListGender = new ArrayList();
	
	LinkedList lListNo = new LinkedList();
	LinkedList lListName = new LinkedList();
	LinkedList lListAge = new LinkedList();
	LinkedList lListGender = new LinkedList();
	
	public void hashtianjia()
	{
		String no = new String(in.nextLine());
		String name = new String(in.nextLine());
		String age = new String(in.nextLine());
		String gender = new String(in.nextLine());
		HashNo.put(no,index);
		HashName.put(name,index);
		HashAge.put(age,index);
		HashGender.put(gender,index);
		index++;
	}
	
	public static String getKey(HashMap map,Integer keys)
	{
         String key = null;
         for(String getKey: map.keySet()){
             if(map.get(getKey).equals(keys)){
                 key = getKey;
             }
         }
         return key;
         //这个key肯定是最后一个满足该条件的key.
	}
	
	public void hashchazhao()
	{
		Integer keys=-1;
		String chazhao = new String(in.nextLine());
		keys = HashNo.get(chazhao);
		if(keys!=-1)
		{
			System.out.println(getKey(HashNo,keys));
			System.out.println(getKey(HashName,keys));
			System.out.println(getKey(HashAge,keys));
			System.out.println(getKey(HashGender,keys));
		}
	}

	public void hashshanchu()
	{
		String chazhao = new String(in.nextLine());
		HashNo.remove(chazhao);
		HashName.remove(chazhao);
		HashAge.remove(chazhao);
		HashGender.remove(chazhao);
	}
	
	public void llisttianjia()
	{
		String no = new String(in.nextLine());
		String name = new String(in.nextLine());
		String age = new String(in.nextLine());
		String gender = new String(in.nextLine());
		lListNo.add(no);
		lListName.add(name);
		lListAge.add(age);
		lListGender.add(gender);
	}
	
	public void llistchahzao()
	{
		String chazhao = new String(in.nextLine());
		for(int i=0;i