Question

I am retrieving data from XLS sheet using jdbc sql. Below is my program.

Case 1:

Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver" );
c = DriverManager.getConnection( "jdbc:odbc:Excel Files", "", "" );
stmnt = c.createStatement();
String query = "select * from [Proficiency$];";
ResultSet rs = stmnt.executeQuery( query );
baseColumnList = new ArrayList();
while( rs.next()) {
    //baseColumnList.add(rs.getString(1));
    System.out.println(rs.getString(1));
    //System.out.println(baseColumnList);
}

output :

Aadmin
Badmin
Badminimage
batch
Cadmin
Dadmin
Eadmin
rulesengine
Fadmin
genadmin
Gadmin
Hdomain-EU
Padmin
IAA

Case 2:

Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver" );
c = DriverManager.getConnection( "jdbc:odbc:Excel Files", "", "" );
stmnt = c.createStatement();
String query = "select * from [Proficiency$];";
ResultSet rs = stmnt.executeQuery( query );
baseColumnList = new ArrayList();
while( rs.next()) {
    baseColumnList.add(rs.getString(1));
    System.out.println(baseColumnList);
}

Output :

[Aadmin]
[Aadmin, Badmin]
[Aadmin, Badmin, Badminimage]
[Aadmin, Badmin, Badminimage, batch]
[Aadmin, Badmin, Badminimage, batch, Cadmin]
[Aadmin, Badmin, Badminimage, batch, Cadmin, Dadmin]
[Aadmin, Badmin, Badminimage, batch, Cadmin, Dadmin, Eadmin]
[Aadmin, Badmin, Badminimage, batch, Cadmin, Dadmin, Eadmin, rulesengine]
[Aadmin, Badmin, Badminimage, batch, Cadmin, Dadmin, Eadmin, rulesengine, Fadmin]
[Aadmin, Badmin, Badminimage, batch, Cadmin, Dadmin, Eadmin, rulesengine, Fadmin, genadmin]
[Aadmin, Badmin, Badminimage, batch, Cadmin, Dadmin, Eadmin, rulesengine, Fadmin, genadmin, Gadmin]
[Aadmin, Badmin, Badminimage, batch, Cadmin, Dadmin, Eadmin, rulesengine, Fadmin, genadmin, Gadmin, Hadmin-EU]
[Aadmin, Badmin, Badminimage, batch, Cadmin, Dadmin, Eadmin, rulesengine, Fadmin, genadmin, Gadmin, Hadmin-EU, Padmin]
[Aadmin, Badmin, Badminimage, batch, Cadmin, Dadmin, Eadmin, rulesengine, Fadmin, genadmin, Gadmin, Hadmin-EU, Padmin, IAA]

Please can anyone explain why arraylist is behaving strangly.

Update : Expected result is first output.

Answer 1

This

System.out.println(baseColumnList);

prints the actual content¹ of the list. The result is not strange at all. The list get’s bigger on each iteration.

---

To repeat the output of your first example:

while( rs.next()) {
  baseColumnList.add(rs.getString(1));
  System.out.println(baseColumnList.get(baseColumnList.size()-1));
}

But that’s nonsense. The following snippet is more elegant:

while( rs.next()) {
  String columnValue = rs.getString(1);
  baseColumnList.add(columnValue);
  System.out.println(columnValue);
}

---

¹ Actually baseColumnList.toString() is called.