public class JPasswordField
extends JTextField

java.lang.Object
 Ｌ java.awt.Component
     Ｌ java.awt.Container
         Ｌ javax.swing.JComponent
             Ｌ javax.swing.text.JTextComponent
                 Ｌ javax.swing.JTextField
                     Ｌ javax.swing.JPasswordField

JPasswordFieldクラスのオブジェクトを作成

JPasswordField
public JPasswordField(int columns)

JTextField pass = new JTextField(20);

サンプルプログラム

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import java.awt.Container;
import java.awt.BorderLayout;

class SSample1_1 extends JFrame{
  public static void main(String args[]){
    SSample1_1 frame = new SSample1_1("タイトル");
    frame.setVisible(true);
  }

  SSample1_1(String title){
    setTitle(title);
    setBounds(100, 100, 300, 250);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JPanel p = new JPanel();

    JPasswordField pass1 = new JPasswordField(20);
    JPasswordField pass2 = new JPasswordField("初期値の設定");

    p.add(pass1);
    p.add(pass2);

    Container contentPane = getContentPane();
    contentPane.add(p, BorderLayout.CENTER);
  }
}

getPassword
public char[] getPassword()

JPasswordField pass = new JPasswordField(20);
char[] password = pass.getPassword();

JPasswordField pass = new JPasswordField(20);
char[] password = pass.getPassword();
String passwordstr = new String(password);

サンプルプログラム

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JLabel;
import javax.swing.JButton;
import javax.swing.JOptionPane;
import java.awt.Container;
import java.awt.BorderLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

class SSample2_1 extends JFrame implements ActionListener{
  JPasswordField pass;

  public static void main(String args[]){
    SSample2_1 frame = new SSample2_1("タイトル");
    frame.setVisible(true);
  }

  SSample2_1(String title){
    setTitle(title);
    setBounds(100, 100, 300, 250);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JPanel p = new JPanel();

    JLabel label = new JLabel("パスワードを入力:");
    pass = new JPasswordField(10);

    JButton button = new JButton("確認");
    button.addActionListener(this);

    p.add(label);
    p.add(pass);
    p.add(button);

    Container contentPane = getContentPane();
    contentPane.add(p, BorderLayout.CENTER);
  }

  public void actionPerformed(ActionEvent e){
    String password = new String(pass.getPassword());

    if (password.equals("0000")){
      JLabel label = new JLabel("認証に成功しました");
      JOptionPane.showMessageDialog(this, label, "成功", JOptionPane.INFORMATION_MESSAGE);
    }else{
      JLabel label = new JLabel("パスワードが違います");
      JOptionPane.showMessageDialog(this, label, "失敗", JOptionPane.ERROR_MESSAGE);
      pass.setText("");
    }
  }
}

setEchoChar
public void setEchoChar(char c)

JPasswordField pass = new JPasswordField(20);
pass.setEchoChar('*');

サンプルプログラム

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import java.awt.Container;
import java.awt.BorderLayout;

class SSample3_1 extends JFrame{
  JPasswordField pass;

  public static void main(String args[]){
    SSample3_1 frame = new SSample3_1("タイトル");
    frame.setVisible(true);
  }

  SSample3_1(String title){
    setTitle(title);
    setBounds(100, 100, 300, 250);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JPanel p = new JPanel();

    JPasswordField pass1 = new JPasswordField(20);
    pass1.setEchoChar('*');
    JPasswordField pass2 = new JPasswordField(20);
    pass2.setEchoChar('秘');

    p.add(pass1);
    p.add(pass2);

    Container contentPane = getContentPane();
    contentPane.add(p, BorderLayout.CENTER);
  }
}