I'm trying to build a GUI that uses a JFileChooser to select a file and store the name of the file in a String[] array. I can't for the life of me get it to work. It keeps throwing the IllegalArgumentException: filenames array needs two filenames in it. Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: filenames array needs two filenames in it.
I have a diff class:
package diff.model;
import java.io.*;
/**
* Determines the difference between two text files on a line-by-line basis.
* Usage: see println's in main method.
*
*/
public class Diff {
// Data members
private static boolean outputToFile;
private static String outputFile;
private static String[] text = new String[]{null};
public static String file1, file2, outputfile;
public static String[] filenames = new String[]{file1, file2, outputfile};
/**
* Constructor for objects of class Diff
*/
public Diff() {
outputToFile = false;
}
/**
* Checks if a file exists or not.
* <p>
* Precondition: A non-null string is passed in.
*
* @param filename
* The filename to see if it exists or not.
* @return true If the file exists and false otherwise.
*/
public boolean fileExists(String filename) {
// Check precondition
if (filename == null) {
throw new IllegalArgumentException("filename is null.");
}
File file = new File(filename);
return file.exists();
}
/**
* Compares two text files line-by-line, displaying any lines that differ.
* <p>
* Precondition: The array has two filenames for the files to
* compare and three filenames if the output is also to go to a file.
*
* @param filenames
* Array that contains the filenames
*/
public static void compareFiles(String[] filenames) {
// Check preconditions
if (filenames.length != 2 && outputToFile==false ) {
throw new IllegalArgumentException("filenames array needs two filenames in it.");
}
else if (filenames.length != 3 && outputToFile==true){
throw new IllegalArgumentException("filenames array needs three filenames in it.");
}
// Open the two input files
try {
// Open the two input files
BufferedReader fin1 = new BufferedReader(new FileReader(
filenames[0]));
BufferedReader fin2 = new BufferedReader(new FileReader(
filenames[1]));
// Set up some local variables to be used when reading in the files
String line1;
String line2;
int nCount = 0;
boolean bContinue = true;
boolean bDifference = false;
// Loop reading in from each file comparing line-by-line
while (bContinue) {
line1 = fin1.readLine();
line2 = fin2.readLine();
// Make sure successfully read a line from each file
if (line1 != null && line2 != null) {
// Update the counter that keeps track of the number of
// lines read
nCount++;
// See if the two lines differ
if (!line1.equals(line2)) {
// The lines differ so set the flag that indicates the
// files are not identical
bDifference = true;
// Set the string to output and output the text
String[] text = { nCount + ": " + line1,
nCount + ": " + line2 };
outputText(text);
} // end if (!line1.equals(line2))
} // end if (line1 != null && line2 != null)
// See if have reached the end of both files
else if (line1 == null && line2 == null) {
// Set the looping flag to false since reached the end of
// both files
bContinue = false;
// See if files are completely identical, if they are then
// output that they are identical
if (!bDifference) {
// Set the string to output and output the text
String[] text = { filenames[0] + " and " + filenames[1]
+ " are identical." };
outputText(text);
}
} else // Reached the end of one of the files
{
// Increment the line counter
nCount++;
int nStart = nCount; // Keep track of what line currently at
// Set that the files are different
bDifference = true;
// Determine which file reached the end of
if (line1 == null) {
// Count the number of remaining lines in file 2
nCount += determineRemainingLines(fin2);
// Set the string to output and output the text
String[] text = { "Lines " + nStart + " - " + nCount
+ " only exist in " + filenames[1] };
outputText(text);
} else {
// Count the number of remaining lines in file 1
nCount += determineRemainingLines(fin1);
// Set the string to output and output the text
String[] text = { "Lines " + nStart + " - " + nCount
+ " only exist in " + filenames[0] };
outputText(text);
}
}
}
// Close the files
fin1.close();
fin2.close();
} // end try
catch (FileNotFoundException fnfx) {
// Should not technically ever get here, because of earlier file
// exists check but will have this code as a safety valve.
System.out
.println("Error: Input file was not found. Exiting program.");
} catch (IOException iox) {
System.err.println(iox.getMessage());
iox.printStackTrace();
}
}
/**
* Output the passed in text to the screen
* <p>
* Precondition: text is not null.
*
* @param text
* [] An array of strings to print out. Each array item is
* printed on a single line.
*
*/
public static void outputText(String[] text) {
// Check precondition
if (text == null) {
throw new IllegalArgumentException("text is null");
}
// Loop through element in the string array and print out each text
// string in the array
for (int i = 0; i < text.length; i++) {
System.out.println(text[i]);
}
// See if need to output the text to a file also
if (outputToFile) {
try {
// Open a file to append to
PrintWriter fileout = new PrintWriter(new BufferedWriter(
new FileWriter(outputFile, true)));
// Loop through the array print out each array element to a
// single line
for (int i = 0; i < text.length; i++) {
fileout.println(text[i]);
} // end for
fileout.close();
} // end try
catch (IOException iox) {
System.err.println(iox.getMessage());
iox.printStackTrace();
}
}
}
/**
* Count the number of remaining lines in the open file.
* <p>
* Precondition: The file is pointing to an open file.
*
* @param file
* File to continue counting lines in
* @return The number of lines from the current point in the file to the end
* of the file.
*/
private static int determineRemainingLines(BufferedReader file) {
if (file == null) {
throw new IllegalArgumentException("file pointer is null.");
}
int nCount = 0;
try {
// Continue reading until end of file counting lines
String line = file.readLine();
while (line != null) {
line = file.readLine();
nCount++;
}
}
catch (IOException iox) {
System.err.println(iox.getMessage());
iox.printStackTrace();
}
return nCount;
}
/**
* @return the filenames
*/
public static String[] getFilenames() {
return filenames;
}
/**
* @param filenames the filenames to set
*/
public static void setFilenames(String[] filenames) {
Diff.filenames = filenames;
}
}
And a DiffGUI class:
import diff.model.Diff;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.text.*;
import java.util.Arrays;
import java.util.Scanner;
import java.awt.Color;
import java.io.*;
import javax.swing.JTextArea;
import javax.swing.border.EmptyBorder;
public class DiffGUI extends JFrame {
private JPanel contentPane;
private final JButton btnFile01 = new JButton("Select File 1");
private final JButton btnFile02 = new JButton("Select File 2");
private final JTextField textField = new JTextField();
private final JTextField textField_1 = new JTextField();
private final JLabel lblFile = new JLabel("File 1:");
private final JLabel lblFile_1 = new JLabel("File 2:");
private final JButton btnCompareFiles = new JButton("Compare Files");
private final JLabel lblOutputFile = new JLabel("Output File:");
private final JTextField textField_2 = new JTextField();
private final JTextArea textArea = new JTextArea();
private String[] filenames;
// Create a new diff object
Diff differ = new Diff();
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
DiffGUI frame = new DiffGUI();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public DiffGUI() {
setTitle("Diff");
setResizable(false);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 600);
this.contentPane = new JPanel();
this.contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(this.contentPane);
this.contentPane.setLayout(null);
this.lblFile.setBounds(17, 6, 44, 16);
this.contentPane.add(this.lblFile);
this.textField.setBounds(61, 0, 265, 28);
this.textField.setColumns(10);
this.contentPane.add(this.textField);
this.btnFile01.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
// Create a file chooser
JFileChooser chooser = new JFileChooser();
// Add filter for .txt files
chooser.addChoosableFileFilter(new FileFilter());
chooser.showOpenDialog(null);
File file1 = chooser.getSelectedFile();
// Write file name to text filed
textField.setText(file1.getName());
// Add file to array filenames
filenames[0] = file1.getName();
}
});
this.btnFile01.setBounds(327, 1, 117, 29);
this.contentPane.add(this.btnFile01);
this.lblFile_1.setBounds(17, 34, 44, 16);
this.contentPane.add(this.lblFile_1);
this.textField_1.setBounds(61, 28, 265, 28);
this.textField_1.setColumns(10);
this.contentPane.add(this.textField_1);
this.btnFile02.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
// Create file chooser
JFileChooser chooser= new JFileChooser();
// Add filter for .txt files
chooser.addChoosableFileFilter(new FileFilter());
chooser.showOpenDialog(null);
File file2 = chooser.getSelectedFile();
// Write file name to text field
textField_1.setText(file2.getName());
// Add file to array filenames
filenames[1] = file2.getName();
}
});
this.btnFile02.setBounds(327, 29, 117, 29);
this.contentPane.add(this.btnFile02);
this.lblOutputFile.setBounds(17, 62, 81, 16);
this.contentPane.add(this.lblOutputFile);
this.textField_2.setBounds(97, 56, 347, 28);
this.textField_2.setColumns(10);
this.contentPane.add(this.textField_2);
this.btnCompareFiles.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
}
});
this.btnCompareFiles.setBounds(149, 94, 149, 43);
this.contentPane.add(this.btnCompareFiles);
this.textArea.setBounds(6, 149, 438, 423);
this.contentPane.add(this.textArea);
}
/**
* @return the filenames
*/
public String[] getFilenames() {
return filenames;
}
/**
* @param filenames the filenames to set
*/
public void setFilenames(String[] filenames) {
this.filenames = filenames;
}
}
