Your code produces a stacktrace
Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 2
at javax.swing.JTable$1.getValueAt(JTable.java:689)
at javax.swing.JTable.getValueAt(JTable.java:2720)
which is a good indicator of the problem. It means that the number of data columns needs to match the number of column identifiers. Add the missing data:
String data[][] = {
{ "NEWDATA", "HEADER 1", "ABC" }, { "NEWDATA", "HEADER 1", "HEADER 1" },
{ "NEWDATA", "HEADER 1", "GHI" }, { "NEWDATA", "HEADER 1", "GHI" },
};
Read: How to Use Tables