package com.student.vo;

public class people {
	private int id;
	private String name;
	private String tel;
	public people(int id,String name,String tel){
		this.id=id;
		this.name=name;
		this.tel=tel;
	}
    @Override
    public boolean equals(Object obj) {
        if(!(obj instanceof people)) {
            return false;
        }
        people b = (people)obj;
        if(this.id == b.id) {
            return true;
        }
        return false;
    }
    
    @Override
    public int hashCode() {
        return id;
    }
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getTel() {
		return tel;
	}
	public void setTel(String tel) {
		this.tel = tel;
	}
}
 

新建一個people類，在類中重寫了HashSet的HashCode、equals方法，讀者寫的時候可以直接把程式碼擷取貼上到你自己想用的類中，HashCode方法中的id相當於主鍵也就是鍵值，只能是唯一的，HashSet為按照這個id判斷是否是同一個物件進行去重操作。

我這邊呼叫是在servlet中引用此類

package com.student.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import java.util.Vector;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.student.dao.impl.UserDAOImpl;
import com.student.factory.DAOFactory;
import com.student.vo.User;
import com.student.vo.people;

public class studentFind extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doPost(request, response);
	}
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=utf-8");
		PrintWriter out=response.getWriter();
		String id=new String(request.getParameter("id").getBytes("iso-8859-1"),"utf-8");
		String username=new String(request.getParameter("username").getBytes("iso-8859-1"),"utf-8");
		//list vector存的值可以重複因此改用set
		Vector<User> vector=new Vector<User>(); 
		Vector<User> vector1=new Vector<User>();
		Vector<User> vector2=new Vector<User>();
		Vector<User> vector3=new Vector<User>();
		//採用hashset儲存自定義的物件，之前試過用treeMap做了兩三個小時都沒有把鍵作為物件儲存，總會報型別轉換錯誤
		try {
				//按照優先順序查詢 姓名、電話號碼、性別
				if(!id.equals("")){
				vector=DAOFactory.getUserDAOinstance().findName(id,username);
				vector1=DAOFactory.getUserDAOinstance().findTel(id,username);
				vector2=DAOFactory.getUserDAOinstance().findSex(id,username);
				vector3=DAOFactory.getUserDAOinstance().findPinyin(id,username);
				Set<people> set = new HashSet<people>();
				for(int i=0;i<vector.size();i++){
					User user=new User();
					user=vector.get(i);
					int yy=Integer.valueOf(user.getId());
					set.add(new people(yy,user.getName(),user.getTel()));
				}
				for(int i=0;i<vector1.size();i++){
					User user=new User();
					user=vector1.get(i);
					int yy=Integer.valueOf(user.getId());
					set.add(new people(yy,user.getName(),user.getTel()));
					//System.out.println(user.getName()+"+"+user.getId());
					
				}
				for(int i=0;i<vector2.size();i++){
					User user=new User();
					user=vector2.get(i);
					int yy=Integer.valueOf(user.getId());
					set.add(new people(yy,user.getName(),user.getTel()));
				}
				for(int i=0;i<vector3.size();i++){
					User user=new User();
					user=vector3.get(i);
					int yy=Integer.valueOf(user.getId());
					set.add(new people(yy,user.getName(),user.getTel()));
				}
		        for(people p : set){
		            System.out.println(p.getName()+"+"+p.getId());
		        }
				request.setAttribute("rs", set);
				request.getRequestDispatcher("ajaxShow.jsp").forward(request, response);
				}
		}
			catch (Exception e) {
				e.printStackTrace();
			}
		}	
	
	}