ArrayList - class java.util.ArrayList.
Resizable-array implementation of the List interface.
BorderLayout - class java.awt.BorderLayout.
          A border layout lays out a container, arranging and resizing its components to fit in five regions: north, south, east, west, and center.
BoxLayout - class javax.swing.BoxLayout.
A layout manager that allows multiple components to be laid out either vertically or horizontally.
Color - class java.awt.Color
        Provides color variables
FileDialog - class java.awt.FileDialog.
The FileDialog class displays a dialog window from which the user can select a file.
FileWriter - class
Convenience class for writing character files.
FlowLayout - class java.awt.FlowLayout.
A flow layout arranges components in a left-to-right flow, much like lines of text in a paragraph.
Graphics - class java.awt.Graphics.
The Graphics class is the abstract base class for all graphics contexts that allow an application to draw onto components that are realized on various devices, as well as onto off-screen images.
GridLayout - class java.awt.GridLayout.
The GridLayout class is a layout manager that lays out a container's components in a rectangular grid.

JApplet - class javax.swing.JApplet.
An extended version of java.applet.Applet that adds support for the JFC/Swing component architecture.
JButton - class javax.swing.JButton.
An implementation of a "push" button.

JFrame - class javax.swing.JFrame.
An extended version of java.awt.Frame that adds support for the JFC/Swing component architecture.
JLabel - class javax.swing.JLabel.
A display area for a short text string or an image, or both.

JScrollPane - class javax.swing.JScrollPane.
Provides a scrollable view of a lightweight component.
JTextArea - class javax.swing.JTextArea.
A JTextArea is a multi-line area that displays plain text.

JTextField - class javax.swing.JTextField.
JTextField is a lightweight component that allows the editing of a single line of text.
Math - class java.lang.Math.
The class Math contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.
MouseAdapter - class java.awt.event.MouseAdapter.
An abstract adapter class for receiving mouse events.
PrintWriter - class
Print formatted representations of objects to a text-output stream.
Random - class java.util.Random.
An instance of this class is used to generate a stream of pseudorandom numbers.
String - class java.lang.String.
The String class represents character strings.
Thread - class java.lang.Thread.
A thread is a thread of execution in a program.

Timer - class javax.swing.Timer.
Fires one or more action events after a specified delay.