Error NullPointerException [closed]

I have a program that performs biometric authentication in two versions:

1) The user selects the binary file via javax.swing as follows:

public class Busca extends javax.swing.JFrame {
   ...
   java.io.FileInputStream fis = null; fis = new            
   Java.io.FileInputStream(fs_at.getSelectedFile()); nLoadLen = fis.read(loadData); 
   int retornoexp = exportEngine.ImportFIR(loadData, nLoadLen, nMinType, hLoadFIR);

2) In the other version, run the program via the command line and the file is passed as a parameter, thus:

public int autentic_python(String arquivo) { 
   ..... 
   fis = new java.io.FileInputStream(arquivo); 
   nLoadLen = fis.read(loadData); 
   int retornoexp = exportEngine.ImportFIR(loadData, nLoadLen, nMinType, hLoadFIR);

The problem is that in the second version it gives the error Java.lang.NullPointerException in the command exportEngine .

What am I doing wrong?