Trying to create table with dynamic rows

Question

First off, I'm a noob. This is a homework assignment I'm working on. I'm trying to create an Amortization Table based on a user's selection of different term/interest rate combinations. I need a table that has four columns: Payment Month 1-12, Monthly Payment Amount, Interest Paid, and Remaining Principle. But I need the rows to change based on the user's selection of a radio button. I have three radio buttons: 7 years at 5.35% interest, 15 years at 5.5% interest, and 30 years at 5.75% interest. I'll need anywhere from 180 rows to 360 rows; one row for each monthly payment.
I'm not sure about my approach to this, but I created a JTable named 'amortTable' and I'm using the DefaultTableModel. I'm using a for loop to step through the calculations until the principle balance is zero. I'm apparently not doing something right, as the data is not populating in the table. Here's the code in question. I didn't post my full code, but let me know if it's needed and I will.
import java.io.*;
import javax.swing.*;
import javax.swing.table.*;
javax.swing.JTable amortTable = new javax.swing.JTable();
javax.swing.JScrollPane jScrollPane1 = new javax.swing.JScrollPane();
private void init Components()
... //extra code omitted
amortTable.setModel(new javax.swing.table.DefaultTableModel(
new Object [][]
{null, null, null, null}
new String []
"Payment No.", "Payment Amount", "Interest Paid", "Remaining Principle"
jScrollPane1.setViewportView(amortTable);
.... //extra code omitted
}//end initComponents
private void calculateButtonActionPerformed(java.awt.event.ActionEvent evt)
... //extra code omitted
while (loanAmount>0)
for (int i = 0; i < 12; i++)
interestPaid = loanAmount * monthlyRate;
principlePaid = monthlyPymt - interestPaid;
loanAmount = loanAmount - principlePaid;
pymtNo = pymt;
amortTable.addRow(new Object[]{pymtNo, monthlyPymt, interestPaid, loanAmount});
}//end for loop
}//end while loop
}//end calculateButtonActionPerformed
My goal was to use the for loop to continue to add rows containing the specified variables to amortTable until the principle balance reached zero.I get a compiler error that says "cannot find symbol / symbol: method addRow(java.lang.Object[]) / location: class javax.swing.JTable). I'm pretty sure it has to do with the fact that the table is located in a different method than the for loop, but I don't know how to check for that. I also don't believe that the problem is with the method itself, but rather a syntax error elsewhere. Any ideas? Or if I'm going about this the wrong way, can someone point me in the right direction?

Answer 1

Hello and welcome. Some observances.
1) You seem to be trying to call addRow on amortTable, a JTable object, and these beasts shouldn't have that method. Rather you would call this method on the DefaultTableModel object held by this JTable.
2) Please read the FAQ to see how to use code tags to make your code readable when posting it here.
3) I find when I have difficulty like this, it is always better to try to solve the problem in a very simple program first and then use that info in the larger program. So in that light, why not create a very simple program that tries to add simple rows to a JTable on button press. Solve your problem here and you've solved it for the big program. Fail to solve it and you can always post the whole simple program here which will be a lot easier for us to read and understand than your big program.
Much luck!