Utility Classes

In this chapter, we will write two utility classes, which will be used to build the user interface.

Files needed for this chapter are:

• ButtonPanel.java
• SwingComp.java

The SwingComp Class

This class is a factory class that can be used to create standard Swing components.

Listing 15.1 SwingComp.java

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

//Factory class used to create swing components
public class SwingComp{

  //private constructor
  private SwingComp(){
	System.out.println("Cannot create object");
  }

  //This method is used to construct a 
  //new JTextField with the specified 
  //number of columns. 
  public static JTextField createTextField(Container con,int col){
	JTextField tf=new JTextField(col);
		
	//add the text field to the specified container.
	con.add(tf);
	return tf;
  }

  //This method is used to construct a new 
  //JTextField with the specified 
  //number of columns. The method adds the textfield to the 
  //specified container and adds the specified listener
  //to the text field.
  public static JTextField createTextField
		(Container con,ActionListener listener,int col){

	JTextField tf=new JTextField(col);
	tf.addActionListener(listener);
	con.add(tf);
	return tf;
  }

  //This method is used to create a button 
  //with the specified text. The method adds 
  //the button to the specified container and adds the 
  //given listener to the button.
  public static JButton createButton(Container con,
		ActionListener al,String text){

	JButton btn=new JButton(text);
	btn.addActionListener(al);
	con.add(btn);
	return btn;
   }

  //This method is used to create a label 
  //with the specified text. The method adds 
  //the label to the specified container.
  public static JLabel createLabel(Container con,String text){

	JLabel lbl=new JLabel(text);
	lbl.setForeground(Color.black);
	con.add(lbl);
	return lbl;
   }

  //This method is used to create a label 
  //with the specified text and alignment. 
  //The method adds the label to the specified container.
  public static JLabel createLabel(Container con,
		String text,int align){

	JLabel lbl=new JLabel(text,align);
	lbl.setForeground(Color.black);
	con.add(lbl);
	return lbl;
   }

  //This method is used to create a menu 
  //item with the specified text. 
  //The method adds the menu item to the specified menu 
  //and adds the given listener to the menu item.
  public static JMenuItem createMenuItems(JMenu mnu,
		ActionListener listener,String text){
	
	JMenuItem mi = new JMenuItem(text);	
	mi.addActionListener(listener);	
	mnu.add(mi);
	return mi; 		
   }

  //This method is used to create a 
  //menu with the given text. The method adds the 
  //menu to the specified menu bar.
  public static JMenu createMenu(JMenuBar mBar, 
			String text){
	 
	 JMenu mnu = new JMenu(text);
	 mBar.add(mnu);
	 return mnu;
  }

  //This method is used to construct a panel. 
  //The method adds the panel object to the given container 
  //using the specified constraints object.
  public static JPanel createPanel(Container cp,
		String placement){
	
	 JPanel panel =new JPanel();
	 cp.add(panel,placement);
	 return panel;
   }

  //This method is used to construct a panel 
  //with the specified layout manager.
  //The method adds the panel object to the given container 
  //using the specified constraints object.
  public static JPanel createPanel(Container cp,
		String placement,LayoutManager manager){
	
	 JPanel panel =new JPanel(manager);
	 cp.add(panel,placement);
	 return panel;
   }
		 
 }