Java Swing | JPasswordField

PasswordField is a part of javax.swing package . The class JPasswordField is a component that allows editing of a single line of text where the view indicates that something was typed by does not show the actual characters. JPasswordField inherits the JTextField class in javax.swing package.
Constructors of the class are :

1. JPasswordField(): constructor that creates a new PasswordField
   
2. JPasswordField(int columns) : constructor that creates a new empty PasswordField with specified number of columns.
   
3. JPasswordField(String Password) : constructor that creates a new empty Password field initialized with the given string.
   
4. JPasswordField(String Password, int columns) : constructor that creates a new empty PasswordField with the given string and a specified number of columns .
   
5. JPasswordField(Document doc, String Password, int columns) : constructor that creates a Passwordfield that uses the given text storage model and the given number of columns. 
   

Commonly used method of JPasswordField :

1. char getEchoChar() : returns the character used for echoing in JPasswordField.
   
2. setEchoChar(char c) : set the echo character for JPasswordField.
   
3. String getPassword() : returns the text contained in JPasswordField.
   
4. String getText() : returns the text contained in JPasswordField.
   

1. Program to enter name and password using JTextField and JPasswordField

Java

// Java Program to enter name and password
// using JTextField and JPasswordField
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
class text extends JFrame implements ActionListener {
    // JTextField
    static JTextField t;

    // JPasswordField
    static JPasswordField pass;

    // JFrame
    static JFrame f;

    // JButton
    static JButton b;

    // label to display text
    static JLabel l;

    // default constructor
    text()
    {
    }

    // main class
    public static void main(String[] args)
    {
        // create a new frame to store text field and button
        f = new JFrame("textfield");

        // create a label to display text
        l = new JLabel("nothing entered");

        // create a new button
        b = new JButton("submit");

        // create a object of the text class
        text te = new text();

        // addActionListener to button
        b.addActionListener(te);

        // create a object of JTextField with 16 columns and initial text
        t = new JTextField("enter name", 16);

        // create a object of passwordField with 16 columns
        pass = new JPasswordField(16);

        // create an object of font type
        Font fo = new Font("Serif", Font.ITALIC, 20);

        // set the font of the textfield
        t.setFont(fo);

        // create a panel to add buttons and textfield
        JPanel p = new JPanel();

        // add buttons and textfield to panel
        p.add(t);
        p.add(pass);
        p.add(b);
        p.add(l);

        // add panel to frame
        f.add(p);

        // set the size of frame
        f.setSize(300, 300);

        f.show();
    }

    // if the button is pressed
    public void actionPerformed(ActionEvent e)
    {
        String s = e.getActionCommand();
        if (s.equals("submit")) {
            // set the text of the label to the text of the field
            l.setText("name = " + t.getText() + "\t Password = " + pass.getText());

            // set the text of field to blank
            t.setText("  ");

            // set the text of password field to blank
            pass.setText("");
        }
    }
}

output :

2. Program to change the echo character of JPasswordField and set initial text for password field

Java

// Java Program to change the echo character of
// JPasswordField and set initial text for password field
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
class text extends JFrame implements ActionListener, FocusListener {
    // JTextField
    static JTextField t;

    // JPasswordField
    static JPasswordField pass;

    // JFrame
    static JFrame f;

    // JButton
    static JButton b;

    // label to display text
    static JLabel l;

    // default constructor
    text()
    {
    }

    // main class
    public static void main(String[] args)
    {
        // create a new frame to store text field and button
        f = new JFrame("textfield");

        // create a label to display text
        l = new JLabel("nothing entered");

        // create a new button
        b = new JButton("submit");

        // create a object of the text class
        text te = new text();

        // addActionListener to button
        b.addActionListener(te);

        // create a object of JTextField with 16 columns and initial text
        t = new JTextField("enter name", 16);

        // create a object of passwordField with 16 columns
        pass = new JPasswordField(16);

        // add FocusListener to passwordField
        pass.addFocusListener(te);

        // set the echo character of the password field
        pass.setEchoChar((char)0);

        // set initial text for password field
        pass.setText("enter password");

        // set the echo character of the password field
        // create an object of font type
        Font fo = new Font("Serif", Font.ITALIC, 20);

        // set the font of the textfield
        t.setFont(fo);

        // create a panel to add buttons and textfield
        JPanel p = new JPanel();

        // add buttons and textfield to panel
        p.add(t);
        p.add(pass);
        p.add(b);
        p.add(l);

        // add panel to frame
        f.add(p);

        // set the size of frame
        f.setSize(300, 300);

        f.show();
    }
    // flag to set the text to blank for the first time when the component gets focus
    boolean flag = true;

    // events of focus listener
    // when focus is gained
    public void focusGained(FocusEvent e)
    {
        if (flag) {
            // set a definite echo char
            pass.setEchoChar('*');

            // only set the text to blank for 1st time
            // set the text to blank
            pass.setText("");
            flag = false;
        }
    }

    // when the focus is lost
    public void focusLost(FocusEvent e)
    {
    }

    // if the button is pressed
    public void actionPerformed(ActionEvent e)
    {
        String s = e.getActionCommand();
        if (s.equals("submit")) {
            // set the text of the label to the text of the field
            l.setText("name = " + t.getText() + "\t, Password = " + pass.getText());

            // set the text of field to blank
            t.setText("  ");

            // set the text of password field to blank
            pass.setText("");
        }
    }
}

Note : The above programs might not run in an online compiler use an offline IDE. 
the default text and number of columns of password can be changed by the programmer as per their need.