Question

Hi while developing one of my web application i am storing the user information in to an ArrayList based on sql query executed, it contain duplicate objects how to remove duplicate objects in list , i already tried some method but it still not working.
This Is My Code Correct me where i am wrong

      public ArrayList loadData() throws ClassNotFoundException, SQLException {
    ArrayList userList = new ArrayList();
    String url = "";
    String dbName = "";
    String userName = "";
    String password = "";
    Connection con = null;
    Class.forName("org.apache.derby.jdbc.ClientDriver");
    con = DriverManager.getConnection(url + dbName, userName, password);
    PreparedStatement ps = null;
    try {
        String name;
        String fatherName;
        int Id;
        String filePath;
        int age;
        String address;
        String query = "SELECT NAME,FATHERNAME,AGE,ADDRESS,ID,FILEPATH FROM USER_INFORMATION ,USER_PHOTO WHERE ID=USER_ID";
        ps = con.prepareStatement(query);
        ResultSet rs = ps.executeQuery();
        while (rs.next()) {
            name = rs.getString(1);
            fatherName = rs.getString(2);
            age = rs.getInt(3);
            address = rs.getString(4);
            Id = rs.getInt(5);
            filePath=rs.getString(6);
           /* if(flag)
            {
                prev=Id;
                flag=false;
            }
            else if(Id==prev)
            {
                TEMP=TEMP+";"+filePath;
            }*/
            //PhotoList = PhotoList(Id, con);
            UserData list = new UserData();
            list.setName(name);
            list.setFatherName(fatherName);
            list.setAge(age);
            list.setAddress(address);
            list.setId(Id);
   //       list.setFilePath(filePath);
            userList.add(list);
        }
        ps.close();
        con.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
    ArrayList al = new ArrayList();
    HashSet hs = new HashSet();
    hs.addAll(userList);
    al.clear();
    al.addAll(hs);
    return al;
}

And My Bean Class contant is

    public class UserData {

private String name;
private String fatherName;
private int Id;
//private String filePath;
private int age;
private String address;
public UserData()
{

}

public UserData(String name, String fatherName,int Id, int age,String address)
{
    this.name = name;
    this.fatherName = fatherName;
    this.Id = Id;
    //this.filePath=filePath;
    this.age=age;
    this.address=address;
}
//GETTER AND SETTER..

Answer 1

If you want a Collection of objects that does not have a specific order and you don’t want duplicates, it’s better for you just to use a Set like for example HashSet, or, if in your set the order is important, the TreeSet.

Just remember to override the hash and equals methods.

if you add this to your bean everything should work:

public int hashCode() {
    return (name + fatherName+ Id + filePath + age + address).hashCode();
}

public boolean equals(Object obj) {
    return ( hashCode() == obj.hashCode() );
}