Thread: I'm sure it is really simple but it is driving me crazy

I am not a great programmer but I need to make a simple rule management system, the problem I am having is that due to the number of options I had to divide it up over two separate JFrames, what I have done so far is that when the' Next' button is clicked it will combine the users input into a single String which works fine but I need to access this String from the new class on the second JFrame at this point it seems what ever I try I end up with a null-point exception.

This is the code for my button (not including any of my poor attempts to pass it over!):

private void cmdnextActionPerformed(java.awt.event.ActionEvent evt) {
ruleHeader = (String)lsbaction.getSelectedItem() + " " + (String)lsbprotocol.getSelectedItem();
 
if (cbsourceipany.isSelected()){
ruleHeader = ruleHeader + " any";
}else{
ruleHeader = ruleHeader + " " + txtsource.getText() + (String)lsbsourcex.getSelectedItem();
}
if (cbsourceportany.isSelected()){
ruleHeader = ruleHeader + " any";
}else{
ruleHeader = ruleHeader + " " + txtsport.getText();
}
 
if (cbdirect.isSelected()) {
ruleHeader = ruleHeader + " <> ";
}else{
ruleHeader = ruleHeader + " -> ";
}
 
if (cbdestipany.isSelected()){
ruleHeader = ruleHeader + " any";
}else{
ruleHeader = ruleHeader + " " + txtdest.getText() + (String)lsbdestx.getSelectedItem();
}
if (cbdestportany.isSelected()){
ruleHeader = ruleHeader + " any";
}else{
ruleHeader = ruleHeader + " " + txtdestport.getText();
}
txttest1.setText(ruleHeader);
 
new Rule_Addition_Options().setVisible(true);
}