Question

Java please answer A and B

a.         Describe the purpose of action listener in push button jbtnCompare.(from the code below)

b.         Explain why there are not action listeners added to text fields of this program.(from the code below)

code

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;

class SwingFC implements ActionListener {

JTextField jtfFirst; // holds the first file name
JTextField jtfSecond; // holds the second file name

JButton jbtnComp; // button to compare the files

JLabel jlabFirst, jlabSecond; // displays prompts
JLabel jlabResult; // displays results and error messages

SwingFC() {

    // Create a new JFrame container.
    JFrame jfrm = new JFrame("Compare Files");

    // Specify FlowLayout for the layout manager.
    jfrm.setLayout(new FlowLayout());

    // Give the frame an initial size.
    jfrm.setSize(200, 190);

    // Terminate the program when the user closes the application.
    jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // Create the text fields for the file names..
    jtfFirst = new JTextField(14);
    jtfSecond = new JTextField(14);

    // Set the action commands for the text fields.
    jtfFirst.setActionCommand("fileA");
    jtfSecond.setActionCommand("fileB");

    // Create the Compare button.
    JButton jbtnComp = new JButton("Compare");

    // Add action listener for the Compare button.
    jbtnComp.addActionListener(this);

    // Create the labels.
    jlabFirst = new JLabel("First file: ");
    jlabSecond = new JLabel("Second file: ");
    jlabResult = new JLabel("");

    // Add the components to the content pane.
    jfrm.add(jlabFirst);
    jfrm.add(jtfFirst);
    jfrm.add(jlabSecond);
    jfrm.add(jtfSecond);
    jfrm.add(jbtnComp);
    jfrm.add(jlabResult);

    // Display the frame.
    jfrm.setVisible(true);
}

// Compare the files when the Compare button is pressed.
public void actionPerformed(ActionEvent ae) {
    int i=0, j=0;

    // First, confirm that both file names have
    // been entered.
    if(jtfFirst.getText().equals("")) {
      jlabResult.setText("First file name missing.");
      return;
    }
    if(jtfSecond.getText().equals("")) {
      jlabResult.setText("Second file name missing.");
      return;
    }

    // Compare files. Use try-with-resources to manage the files.
    try (FileInputStream f1 = new FileInputStream(jtfFirst.getText());
         FileInputStream f2 = new FileInputStream(jtfSecond.getText()))
    {
      // Check the contents of each file.
      do {
        i = f1.read();
        j = f2.read();
        if(i != j) break;
      } while(i != -1 && j != -1);

      if(i != j)
        jlabResult.setText("Files are not the same.");
      else
        jlabResult.setText("Files compare equal.");
    } catch(IOException exc) {
      jlabResult.setText("File Error");
    }
}

public static void main(String args[]) {
    // Create the frame on the event dispatching thread.
    SwingUtilities.invokeLater(new Runnable() {
      public void run() {
        new SwingFC();
      }
    });
}
}

Answer 1

A) Describe the purpose of action listener in push button jbtnCompare.(from the code below)

jbtnCompare Button implements an action listener to define what should be done when a user performs a certain operation. for example when a user clicks jbtnCompare Button. Two file name which are in the textfield are open and checked if their content matches then it shows the message Files compare equal and when not shows message Files are not the same."

B) Explain why there are not action listeners added to text fields of this program.(from the code below)

we do not add the action listener to text fields as because we need text only (file names) to check if the content is equal we do not need to occur any event while getting the text in text fields.

/* PLEASE UPVOTE (THANK YOU IN ADVANCE) */