The Java language provides toolkits to build rich Graphical User Interfaces (GUI). AWT and Swing are two of them.
 AWT
The Java programming language class library provides a user interface toolkit called the Abstract Windowing Toolkit, or the AWT. The user interface is that part of a program that interacts with the user of the program.
Because the Java programming language is platform-independent, the AWT must also be platform-independent. The AWT was designed to provide a common set of tools for graphical user interface design that work on a variety of platforms. The user interface elements provided by the AWT are implemented using each platform's native GUI toolkit, thereby preserving the look and feel of each platform. This is one of the AWT's strongest points. The disadvantage of such an approach is the fact that a graphical user interface designed on one platform may look a little different when displayed on another platform.

Components and containers

A graphical user interface is built of graphical elements called components. Typical components include such items as buttons, scrollbars, and text fields. Components allow the user to interact with the program and provide the user with visual feedback about the state of the program. In the AWT, all user interface components are instances of class Component or one of its subtypes.



Components do not stand alone, but rather are found within containers. Containers contain and control the layout of components. Containers are themselves components, and can thus be placed inside other containers.

Window:  A top-level display surface (a window). An instance of the Window class is not attached to nor embedded within another container. An instance of the Window class has no border and no title.
Frame: A top-level display surface (a window) with a border and title. An instance of the Frame class may have a menu bar. It is otherwise very much like an instance of the Window class.

Swing

Swing is a GUI widget toolkit for Java. It is built on top of the AWT API. Also, it is a part of Oracle’s Java Foundation Classes (JFC). Furthermore, Swing provides basic components such as labels, textboxes, buttons, etc. as well as advanced components such as tabbed panes, table, and, trees. Therefore, Swing provides more sophisticated components than AWT. Here, the programmer has to import javax.swing package to write a Swing application.

The main differences between AWT and Swing (taken from  www.pediaa.com) :

Component                                                                        AWT

      Label                                                                             AWT

      Container                                                                     AWT

             JComponent

                   JLabel

                   JComboBox

                   AbstractButton

                         JButton

                         JToggleButton

                                JCheckBox

                                JRadioButton

                   JMenuItem

                         JMenu

                         JCheckBoxMenuItem

                   JMenuBar

                   JPanel

                   JToolBar

                   JScrollPane

                   JTabbedPane

                   JSplitPane

                   JTextComponent

                         JTextField

                         JTextArea

                         JEditorPane

                   JList

                   JTree

                   JTable

             Window                                                                  AWT

                   Frame                                                               AWT

                         JFrame

                   Dialog                                                              AWT

                         JDialog

                   Jwindow

  JFrame

import javax.swing.* ;
public class Window1 {
         public static void main (String args[]){
                JFrame wd = new JFrame() ;
                wd.setSize (250, 100) ;
                wd.setTitle ("graphic window") ;
                wd.setVisible (true) ;
         }
}


wd.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE); 
wd.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);                        // default)
wd.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); 
wd.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

Modifications on the JFrame

import javax.swing.* ;
public class MyFrame extends JFrame{
    MyFrame(int x, int y, int ln, int ht){
        this.setBounds(x, y, ln, ht);
        this.setVisible(true);
        this. setTitle ("graphic window") ;
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

import java.util.*;
public class Test1 {
    public static void main(String arg[]){
        Scanner in = new Scanner(System.in);
        MyFrame mf = new MyFrame(50,80,300,250);
        System.out.print("new frame created, enter to change dimensions");
        in.nextLine();
        mf.setSize (350, 300) ;
       
        System.out.print("new name: ");
        String s = in.nextLine();
        mf.setTitle (s);       
        System.out.println("boundaries modified ");
        mf.setBounds(60,45,350,220);      //x, y of the upper left corner, length, height
       
        System.out.print("new length ");
        int ln= Integer.parseInt(in.nextLine());
        System.out.print("new height ");
        int height= Integer.parseInt(in.nextLine());
        mf.setSize (ln,height);
        System.out.print("enter to make invisible:");
        in.nextLine();
        mf.setVisible(false);
        System.out.print("enter to make visible:");
        in.nextLine();
        mf.setVisible(true);
        System.out.print("enter to finish program");
        in.nextLine();
        System.exit(1);
    }
}

Mouse in the JFrame

class MyMouse implements MouseListener {
         public void mouseClicked (MouseEvent ev) { ..... }
         public void mousePressed (MouseEvent ev) { ..... }
         public void mouseReleased(MouseEvent ev) { ..... }
         public void mouseEntered (MouseEvent ev) { ..... }
         public void mouseExited (MouseEvent ev) { ..... }

}

Using an inner class for a listener
----------------

import java.awt.event.*;
import javax.swing.* ;
public class MyFrame extends JFrame{
    private static final long serialVersionUID = 1L;
    JLabel l;
    MyFrame(int x, int y, int ln, int ht){
        this.setBounds(x, y, ln, ht);       
        this.addMouseListener(new MyMouse());  
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        l=new JLabel("to show mouse events",JLabel.CENTER);
        add(l);
        this.setVisible(true);
    }
     public class MyMouse implements MouseListener{
        public void mouseClicked(MouseEvent ev) {
            int x = ev.getX(); int y=ev.getY();
            int xabs=ev.getXOnScreen(); int yabs=ev.getYOnScreen();
            l.setText("in: x= "+x+ " y="+y+" ("+xabs+","+yabs+") on screen");
            if(ev.getClickCount()==2) l.setText(l.getText()+" double clicked");
        }
        public void mousePressed (MouseEvent ev) {}
        public void mouseReleased(MouseEvent ev) {}
        public void mouseEntered (MouseEvent ev) {
            l.setText("mouse in");
        }
        public void mouseExited (MouseEvent ev) {
            l.setText("mouse out");
        }
    }
}

public class Test {
    public static void main(String arg[]){
        new MyFrame(50,80,400,350);
    }
} 

Adapter

class MouseAdapter implements MouseListener {
         public void mouseClicked (MouseEvent ev) {}
         public void mousePressed (MouseEvent ev) {}
         public void mouseReleased(MouseEvent ev) {}
         public void mouseEntered (MouseEvent ev) {}
         public void mouseExited (MouseEvent ev) {}
}

--------------------

public class MyMouse extends MouseAdapter {
         public void mouseClicked(MouseEvent ev) {
                System.out.println("x="+ev.getX() + " y="+ ev.getY());
         }
         public void mouseEntered (MouseEvent ev) {
                System.out.println("mouse in");
         }
         public void mouseExited (MouseEvent ev) {
                System.out.println("mouse out");
         }
}

JButton, Layout

import javax.swing.* ;
public class MyFrame extends JFrame{ 
    MyFrame(String name,int x, int y, int ln, int ht){
        this.setBounds(x, y, ln, ht);
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setTitle(name);
    }
}

import javax.swing.*;
public class Test {
    public static void main(String arg[]){
        MyFrame mf = new MyFrame("ButtonOne",50,80,200,150);
        JButton bt1 = new JButton("butt1");
        mf.add(bt1);                       // default Layout
        mf.validate();                     // validate the container
    }
}

setLayout

import java.awt.*;
import javax.swing.*;
public class Test {
    public static void main(String arg[]){
        MyFrame mf =
             new MyFrame("ButtonOne",50,80,200,150);
        mf.setLayout(new FlowLayout());     
        JButton bt1 = new JButton("butt1");
        JButton bt2 = new JButton("butt2");
        mf.add(bt1);
        mf.add(bt2);
        mf.validate();
    }
}

Listener

import javax.swing.* ;
public class MyFrame extends JFrame{ 
    MyFrame(String name,int x, int y, int ln, int ht){
        this.setBounds(x, y, ln, ht);
        this.setVisible(true);
        this.setTitle(name);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}
-------------------------
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Test {
    static int cnt1=0,cnt2=0;
    public static void main(String arg[]){
        MyFrame mf = new MyFrame("ButtonOne",50,80,200,150);
        mf.setLayout(new FlowLayout());
        JButton bt1 = new JButton("butt1");     JButton bt2 = new JButton("butt2");
        mf.add(bt1);             
        mf.add(bt2);
        bt1.addActionListener(new Bt1());
        bt2.addActionListener(new Bt2());
        mf.validate();
    }
    static class Bt1 implements ActionListener{
        public void actionPerformed(ActionEvent ev){
            System.out.println("butt1: "+ ++cnt1+" times clicked");           
        }
    }
    static class Bt2 implements ActionListener{
        public void actionPerformed(ActionEvent ev){
            System.out.println("butt2: "+ ++cnt2+" times clicked");           
        }
    }
}

getSource() (can be used for all components)

import javax.swing.* ;
public class MyFrame extends JFrame{ 
    MyFrame(String name,int x, int y, int ln, int ht){
        this.setBounds(x, y, ln, ht);
        this.setVisible(true);
        this.setTitle(name);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}
----------------------------------------------------------
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Test1 {
    static int cnt1=0,cnt2=0;
    static JButton bt1,bt2;
    static Bt btLs;
    public static void main(String arg[]){
        MyFrame mf = new MyFrame("One Listener",50,80,200,150);
        mf.setLayout(new FlowLayout());
        bt1 = new JButton("butt1");
        bt2 = new JButton("butt2");
        mf.add(bt1);
        mf.add(bt2);
        btLs = new Bt();
        bt1.addActionListener(btLs);
        bt2.addActionListener(btLs);
        mf.validate();
    }
    static class Bt implements ActionListener{
        public void actionPerformed(ActionEvent ev){
            if (ev.getSource() == bt1){
                System.out.println("butt1: "+ ++cnt1+" times clicked");
            }
            if (ev.getSource() == bt2){
                System.out.println("butt2: "+ ++cnt2+" times clicked");
            }
        }
    }
}

getActionCommand()  

(for the components with command string - Button, Check boxes, Menu Item ... )

static class Bt implements ActionListener{
    public void actionPerformed(ActionEvent ev){
        if (ev.getActionCommand().equals("butt1")){
            System.out.println("butt1: "+ ++cnt1+" times clicked");
        }
        if (ev.getActionCommand().equals("butt2")){
            System.out.println("butt2: "+ ++cnt2+" times clicked");
        }
    }
}

Frame as Listener

import java.awt.event.*;
import javax.swing.* ;
public class MyFrame extends JFrame implements ActionListener{ 
    int cnt1,cnt2;
    MyFrame(String name,int x, int y, int ln, int ht){
        this.setBounds(x, y, ln, ht);
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setTitle(name);
        cnt1=cnt2=0;
    }
    public void actionPerformed(ActionEvent ev){
        if (ev.getActionCommand().equals("butt1")){
            System.out.println("butt1: "+ ++cnt1+" times clicked");
        }
        if (ev.getActionCommand().equals("butt2")){
            System.out.println("butt2: "+ ++cnt2+" times clicked");
        }
    }
}

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class Test {
    static int cnt1=0,cnt2=0;
    public static void main(String arg[]){
        MyFrame mf = new MyFrame("ButtonOne",50,80,200,150);
        mf.setLayout(new FlowLayout());
        JButton bt1 = new JButton("butt1");
        JButton bt2 = new JButton("butt2");
        mf.add(bt1);
        mf.add(bt2);
        bt1.addActionListener(mf);
        bt2.addActionListener(mf);
        mf.validate();
    }
}

Add and remove components

needs 

import java.awt.event.*;
import javax.swing.* ;
public class MyFrame extends JFrame{ 
    MyFrame(String name,int x, int y, int ln, int ht){
        this.setBounds(x, y, ln, ht);
        this.setVisible(true);
        this.setTitle(name);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}
----------------------------------------------------
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Test {
    static JButton bt=null;
    static MyFrame mf=null,mfc=null;
    public static void main(String arg[]){
        mfc = new MyFrame("ButtonControl",10,80,200,150);
        mfc.setLayout(new FlowLayout());
        mf = new MyFrame("Buttons",10,250,200,150);
        mf.setLayout(new FlowLayout());
        JButton btc1=new JButton("add a new button");
        btc1.addActionListener(new AdBt());
        mfc.add(btc1);
        JButton btc2 = new JButton("remove the button"); 
        btc2.addActionListener(new RmBt());
        mfc.add(btc2);
        mfc.validate();
    }
    static class AdBt implements ActionListener{        
        public void actionPerformed(ActionEvent arg0) {
            if(bt == null){
                bt = new JButton("added button");
                mf.add(bt);
                mf.validate(); //or bt.revalidate();
            }            
        }
    }
    static class RmBt implements ActionListener{        
        public void actionPerformed(ActionEvent arg0) {
            if(bt != null){
                mf.remove(bt);
                mf.setVisible(false);
                mf.setVisible(true);   // or mf.repaint();
                bt = null;
            }
        }
    }
}

setEnabled(true/false), Listeners with constructors

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MyFrame extends JFrame{
    MyFrame(String name){
        this.setBounds(200, 250, 250, 200);
        this.setVisible(true);
        this.setTitle(name);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}
//----------------------------------------------------
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Test {
    static JButton bt[];
    public static void main(String arg[]){
        MyFrame mf = new MyFrame("activate/desactivate");
        bt = new JButton[4];
        mf.setLayout(new FlowLayout());
        Activ act = new Activ();
        bt[0]= new JButton("activate all");
        mf.add(bt[0]);
        bt[0].addActionListener(act);
        for(int i=1;i<bt.length;i++){
            bt[i]= new JButton("desactivate "+ i);
            mf.add(bt[i]);
            bt[i].addActionListener(new Desactiv(i));
        }
        mf.validate();
    }
    static class Desactiv implements ActionListener{
        int n;
        Desactiv(int n){     this.n = n; }   //Constructor
        public void actionPerformed(ActionEvent ev) {
            bt[n].setEnabled (false) ;         
        }        
    }
    static class Activ implements ActionListener{        
        public void actionPerformed(ActionEvent ev) {
            for(int i = 1; i<bt.length; i++){
                bt[i].setEnabled (true) ; 
            }                        
        }        
    }
}

JPanel

import java.awt.event.*;
import javax.swing.* ;
public class MyFrame extends JFrame{ 
    MyFrame(String name,int x, int y, int ln, int ht){
        this.setBounds(x, y, ln, ht);
        this.setVisible(true);
        this.setTitle(name);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}
----------------------------------------------------
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Test {
    static Button bt1,bt2,bt3,bt4;
    static JPanel jp1,jp2;
    public static void main(String arg[]){
        MyFrame mfc=new MyFrame(
                        "ButtonControl",10,80,200,150);
        mfc.setLayout(new FlowLayout());
        jp1 = new JPanel(new FlowLayout());
        jp2 = new JPanel(new FlowLayout());
        jp1.setBackground(Color.yellow);
        jp2.setBackground(Color.green);
        mfc.add(jp1);
        mfc.add(jp2);
        bt1 = new Button("show green");
        bt2 = new Button("hide green");
        bt3 = new Button("show yellow");
        bt4 = new Button("hide yellow");
        jp1.add(bt1); jp1.add(bt2);
        jp2.add(bt3); jp2.add(bt4);
        bt1.addActionListener(new Show(2));
        bt2.addActionListener(new Hide(2));
        bt3.addActionListener(new Show(1));
        bt4.addActionListener(new Hide(1));
        mfc.validate();
    }
    static class Hide implements ActionListener{
        int npan;
        Hide(int i){this.npan = i;}         // Constructor
        public void actionPerformed(ActionEvent ev) {
            if(npan == 1)jp1.setVisible(false);
            else jp2.setVisible(false);
        }
    }
    static class Show implements ActionListener{
        int npan;
        Show(int i){    this.npan =i;}     //Constructor
        public void actionPerformed(ActionEvent ev) {
            if(npan == 1)jp1.setVisible(true);
            else jp2.setVisible(true);                    }
    }
}

Check boxes

import java.awt.*;
import javax.swing.* ;
public class MyFrame extends JFrame{
    MyFrame(String name){
        this.setBounds(10, 10, 150, 120);
        this.setVisible(true);
        this.setLayout(new FlowLayout());
        this.setTitle(name);
        this. setDefaultCloseOperation(EXIT_ON_CLOSE);
    }
}
-----------------------------------------------------------------------------
import java.awt.*;
import java.awt.event.*;
import javax.swing.* ;
public class Test {
    static JCheckBox chck1,chck2;
    static Vrfy vr = new Vrfy();
    public static void main(String arg[]){
        MyFrame fm=new MyFrame("Chck");
        chck1 = new JCheckBox ("Test",true) ;
        JButton bt1 = new JButton("vrfy");
        chck2 = new JCheckBox ("Test 1") ;    

        JButton bt2 = new JButton("cnvrt");
        fm.add(chck1);
        fm.add(bt1);
        fm.add(chck2);
        fm.add(bt2);
        chck1.addActionListener(vr);  //Action  listener
        chck2.addItemListener(new Vrfy1()); //Item State changed listener
        bt1.addActionListener(vr);
        bt2.addActionListener(new Cnvrt());
        fm.getContentPane().validate();
    }
    static class Vrfy implements ActionListener{
        public void actionPerformed(ActionEvent ev){
            System.out.print("Ev_lsn_chck1:"+chck1.isSelected());
            System.out.println("\tEv_lsn_chck2:"+chck2.isSelected()+"\n");
        }
    }
    static class Vrfy1 implements ItemListener{
        public void itemStateChanged (ItemEvent ev){
            System.out.print("It_lsn_chck1:"+chck1.isSelected());
            System.out.println("\tIt_lsn_chck2:"+chck2.isSelected()+"\n");
        }
    }
    static class Cnvrt implements ActionListener{
        public void actionPerformed(ActionEvent ev){
            if (chck1.isSelected())chck1.setSelected(false);
            else chck1.setSelected(true);
            if (chck2.isSelected())chck2.setSelected(false);
            else chck2.setSelected(true);            
        }
    }
}

ItemListeners are notified when ever the state of the button is changed, whether through a user interacting with the button or programmatically (via the setSelected method). ActionListeners on the other hand will be called when a user interacts with the button (but can be simulated programmatically via the onClick method).

Note that a user interacting with the button such as clicking or hitting the space bar will also change the state of the button and raise an item event as well as an action event. Generally, you will want to define either one or the other, don't listen for both action events and item events on the button.


Text Fields, Text Areas

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MyFrame extends JFrame implements ActionListener,FocusListener{
    JTextField tf1,tf2,tf3;
    JTextArea ta;
    MyFrame(){                                   
        this.setSize(300,300);
        this.setLayout(new FlowLayout());
        tf1 = new JTextField("initial", 10);   
        tf2 = new JTextField(10);
        tf3 = new JTextField(10);
        ta = new JTextArea(15,10);
        tf2.setEditable(false);                   
        this.add(tf1);       
        this.add(tf2);
        this.add(tf3);
        this.add(ta);
        tf3.addActionListener(new AdTa());
        tf1.addActionListener(this) ;           
        tf1.addFocusListener(this) ;    
        this.setVisible(true);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    }  
    public void actionPerformed(ActionEvent ev){
        tf2.setText(tf1.getText());
    }
    public void focusGained (FocusEvent e){
        System.out.println("Get focus tf1");      
    }
    public void focusLost (FocusEvent e){
        System.out.println("Lost focus tf1");
    }
    class AdTa implements ActionListener{
        public void actionPerformed(ActionEvent arg0) {
            ta.append(tf3.getText()+"\n");
            tf3.setText("");           
        }      
    }
    public static void main(String arg[]){
        MyFrame mf = new MyFrame();      
    }
}

JMenu with  JTextFields, RadioButtons, CheckBoxes, tooltips

import java.awt.*;
import java.awt.event.* ;
import javax.swing.* ;
class MyMenu extends JFrame {
    JMenuBar mb;
    JTextField t;
    public MyMenu () {
        setTitle ("Menu example") ;
        setSize (400, 440) ;
        t = new JTextField(3);
        setLayout(new FlowLayout());
        add(t);
        ActionListener al = new ActionListener() {
            public void actionPerformed(ActionEvent ev){
                t.setText(
                        ((JMenuItem)ev.getSource()).getText());
            }
        };   
        mb = new JMenuBar() ;
        JMenu[] menus = { new JMenu("menu 1"),
            new JMenu("menu 2"), new JMenu("menu 3")};
        for(int i = 0; i < menus.length; i++)
            mb.add(menus[i]);
        setJMenuBar(mb);
        JMenuItem[] items = {
            new JMenuItem("it1"), new JMenuItem("it2")};
        for(int i = 0; i < items.length; i++){
            items[i].addActionListener(al);
            menus[0].add(items[i]);
        }
        menus[0].addSeparator();
        ButtonGroup group = new ButtonGroup() ;
        JRadioButtonMenuItem bt[] = {
            new JRadioButtonMenuItem("bt1"),
            new JRadioButtonMenuItem("bt2")};
         bt[0].setToolTipText ("attention - radio button!") ; // tooltip
        for(int i = 0; i < bt.length; i++){
            group.add(bt[i]);
            bt[i].addActionListener(al);
            menus[0].add(bt[i]);
        }
        menus[0].addSeparator();
        JCheckBoxMenuItem cb[]= {new JCheckBoxMenuItem("chk1"),
            new JCheckBoxMenuItem("chk2"),new JCheckBoxMenuItem("chk3")};
        for(int i = 0; i < cb.length; i++){
            menus[0].add(cb[i]);
            cb[i].addActionListener(al);
        }
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.setVisible(true);
    }
    public static void main(String arg[]){
        MyMenu fm = new MyMenu();
    }
}

getScreenSize()

import javax.swing.* ;
import java.awt.*;
class MyFrame extends JFrame{
    MyFrame ()         {
        this.setTitle ("Example screen size") ;
        Toolkit tk = Toolkit.getDefaultToolkit() ;
        Dimension dimScr = tk.getScreenSize() ;
        this.setSize (dimScr.width/2, dimScr.height/2) ;
        this.setVisible(true);
    }
}
public class Test {
    public static void main(String arg[]){
        MyFrame mf = new MyFrame();
        Dimension dimFrame = mf.getSize();
        System.out.println(dimFrame.width+":"+dimFrame.height);
    }
}



Using FontMetrics

import java.awt.*;
import javax.swing.*;
public class Disposition  extends JFrame{
    MyPanel pan;
    public Disposition(){
        setTitle ("Disposition") ;
        setSize (380, 220) ;
        pan = new MyPanel();
        add(pan);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);
    }
    class MyPanel extends JPanel{
        public void paintComponent(Graphics g){
            super.paintComponent(g) ;
            int x=10,y=10;
            String s[] = {"one ","two ","three "};
            FontMetrics fm = g.getFontMetrics();
            for(int i =0;i<s.length;i++){
                g.drawString( s[i],x, y);
                x+=fm.stringWidth(s[i]);
            }
            x=10;
            for(int i =0;i<s.length;i++){
                y+=fm.getHeight();
                g.drawString( s[i],x, y);
            }
        }
    }
    public static void main(String arg[]){
        Disposition d = new Disposition();
    }
}


Using Font

A font is characterised by
- family name  (Helvetica, Arial, Times Roman ...) ;
- style (Plain, Italic, Bold );
- size (in typografic units, non in pixels)

import javax.swing.* ;
import java.awt.* ;
class MyFont extends JFrame {
    JPanel pan;
    MyFont (){
        setTitle ("Fonts") ;
        setSize (320, 150) ;
        pan = new MyPanel() ;
        add(pan) ;
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);
    }    

    class MyPanel extends JPanel {
        public void paintComponent(Graphics g){
            super.paintComponent(g) ;
            FontMetrics fm = g.getFontMetrics() ;
            String fnts[] = GraphicsEnvironment.getLocalGraphicsEnvironment()
                    .getAvailableFontFamilyNames() ;
            int x=10, y=20;
            g.drawString("by default: "+g.getFont().getFontName()+
                    g.getFont().getSize(),x,y);                                         //default font
            y+=fm.getHeight()+10;
            Font fn = new Font ("Serif", Font.BOLD+Font.ITALIC, 20) ;        
            g.setFont(fn);
            g.drawString (fn.getFontName()+" "+fn.getSize(), x, y) ;
            fn = new Font(fnts[3],Font.PLAIN, 25);                                
            y+=fm.getHeight()+10;
            g.setFont(fn);
            g.drawString (fn.getFontName()+" "+fn.getSize(), x, y) ;
        }
    }

    public static void main(String arg[]){
        new MyFont();
    }
}