Question

I’m trying to do a arraylist of a hashtable for that i did:

ArrayList<java.util.Hashtable<String, String>> info = new ArrayList<java.util.Hashtable<String, String>>();

this did the job but later i needed to add some hashtables inside info using a for cycle:

java.util.Hashtable<String, String> e = new java.util.Hashtable<String, String>();
while(rs.next()){
    e.clear();
    for(String a:dados){
        e.put(a,rs.getString(a));                       
    }
    info.add(e);    
}

The problem is that method add doesnt copy e to info, it only define a pointer to e so when i update e all inserted elements gets the new e values.

Can anyone give some help ?

thx for your time.

Answer 1

This should work:

import java.util.ArrayList;
import java.util.Hashtable;
import java.util.Map;
import java.util.List;

List<Map<String, String>> info = new ArrayList<Map<String, String>>();

while (rs.next()) {
    Map<String, String> e = new Hashtable<String, String>();
    e.clear();
    for (String a : dados) {
        e.put(a, rs.getString(a));
    }
    info.add(e);
}

You should try to avoid declaring collections by their implementation class (declare them as List instead of ArrayList, or Map instead of Hashtable).