Thread: How to do simple formatting in java times tables?

Here is my code

import javax.swing.*;
 
public class lab8a
{
  int rc = 0;
 
 
public static void main(String[] args)
{
    lab8a t = new lab8a();
    t.process();
}
 
 
int process()
{
    boolean keepgoing = true;
    while(keepgoing)
    {
        rc = userPrompt();
        if(rc == 0)
        {
            keepgoing = false;
            continue;
        }
        rc = calcTable(rc);
    } //End of while
    return rc;
} //End of method
 
 
int calcTable(int n)
{
    int width = n;
    int length = n;
 
    int i,j;
    int threeD[][] = new int[length][width];
    for (i=0; i < length; i++)
    {
 
        System.out.println("");
 
        for(j=0; j < width; j++)
        {
 
 
            {
 
                threeD[i][j]= (i+1)*(j+1);
 
 
 
                System.out.printf("%4d ",threeD[i][j]);
                System.out.printf("%4d ",threeD[i] + "|");
                System.out.printf("%4d ",threeD[j] + "_");
 
            }
 
        }
    }
    return 0;
} //End of method
 
 
public int userPrompt()
{
    String ans = JOptionPane.showInputDialog(null,
            "Please enter a number between 1 and 32");
    if (ans == null)
    {
        return 0;
    }
    else
    {
        int n = Integer.parseInt(ans);
        return n;
    }
}
 
}

im working with in java, i'm trying to figure out how to get a nice border around the first row and column in my times table. Something like "|" and "_" . Any ideas?
I put the formatting under the System.out.println but it is giving me these errors
Exception in thread "main" java.util.IllegalFormatConversionException: d != java.lang.String
at java.util.Formatter$FormatSpecifier.failConversion (Formatter.java:3999)
at java.util.Formatter$FormatSpecifier.printInteger(F ormatter.java:2709)
at java.util.Formatter$FormatSpecifier.print(Formatte r.java:2661)
at java.util.Formatter.format(Formatter.java:2433)
at java.io.PrintStream.format(PrintStream.java:920)
at java.io.PrintStream.printf(PrintStream.java:821)
at lab8a.calcTable(lab8a.java:55)
at lab8a.process(lab8a.java:26)
at lab8a.main(lab8a.java:11)