Exercise: Write a program that implements ArrayList
(1)[America] (2)[Canada, America] (3)[Canada, America, Russia] (4)[Canada, America, Russia, France] (5)[Canada, America, Germany, Russia, France] (6)[Canada, America, Germany, Russia, France, India] (7)[America, Germany, Russia, France, India] (8)[America, Germany, France, India] (9)[America, Germany, France]
Download Code: ArrayList Implementation
Exercise: Write a program that count the occurrences of words in a String.
and : 1 day : 1 fun : 1 good : 1 great : 1 have : 2 keep : 1 learning : 1 morning : 1
Download Code: Count Words
Eight Queens problem is to find a solution o place a queen in each row on a chess board such that no two queens attach each other
Exercise: Use recursion to write a program that finds a solution to Eight Queens problem.
Download Code: Eight Queens
Sierpinski triangle is created as follows:
Exercise: Use recursion to write a program that creates Sierpinski triangles of the order which is input by the user.
Download Code: Sierpinski Triangle
Towers of Hanoi is a classic recursion problem. The problem involves moving a specified number of disks of distinct sizes from one tower to another while observing the following rules.
The objectve of the problem is to move all the disks from A to B with the assistance of C.
Exercise: Use recursion to write a program that will take user input for number of disks and solve the problem for that number of disks.
Enter the number of disks:3 The moves are: Move disk 1 from A to B Move disk 2 from A to C Move disk 1 from B to C Move disk 3 from A to B Move disk 1 from C to A Move disk 2 from C to B Move disk 1 from A to B
Download Code: Towers of Hanoi
Exercise: Use recursion to write a program that will determine the size of a given directory.
Enter a file or directory: C:\Users\Maya\Favorites 17711 bytes. Enter a file or directory: C:\Users\Maya\Desktop\aneesh\Java Exercises\Bouncing Ball.png 26651 bytes. Enter a file or directory: C:\Users\Maya\Desktop\aneesh\Java Exercises\No File.txt 0 bytes.
Download Code: Directory Size
Exercise: Write a program that uses selection sort with recursion to sort a list.
Before sort: 2.0 5.0 3.0 1.2 9.8 3.0 After sort: 1.2 2.0 3.0 3.0 5.0 9.8
Download Code: Recursive Selection Sort
Exercise: Write a program that determines whether a String is a Palindrome. Use recursion.
Is moon a Palindrome: false Is noon a Palindrome: true
Download Code: Palindrome Using Recursion
Exercise: Write a program that asks user input for a positive integer and then print the Fibonacci number for that index. Use recursion.
Enter the Fibonacci Index: 7 Fibonacci at index 7 is 13
Download Code: Fibonacci Using Recursion
Exercise: Write a program that asks user input for a positive integer and then print the factorial of the input. The program should use recursion to determine factorial.
Enter a non-negative number 10 Factorial of 10 is 3628800
Download Code: Factorial Using Recursion
RandomAccessFile class allows a file to be read from or written to at random locations. Constructor takes String arguments "r"/"rw" for read only/read-write access to file. The method seek(int) can be used to place the pointer where the read and write can be done.
Exercise: Write a program that demonstrates RandomAccessFile
Current file length is 800 First number is 0 Second number is 1 Tenth number is 9 Modifying the eleventh number to 555 Current file length is 800 Eleventh number is 555
Download Code: Random Access File
ObjectInput/OutputStreams can be used to read and write objects. These are filter streams that can completely replace data stream because it has all the functions available in the data streams like reading and writing integer, double, UTF etc. Apart from those, this also has functionality to read and write objects.
However, please note that only Serializable objects (Classes or super classes of which implements Serializable interface) can be read or written to file.
Exercise: Write a program that uses object streams to read and write objects.
John 85.5 Sat Dec 22 13:56:00 IST 2012
Download Code: Object Stream Demo
BufferedInput/OutputStreams help performance by reducing the read and write from/to files. These are filter streams that read to or write from a byte array instead of doing it one by one.
Exercise: Write a program that uses buffered streams to copy a file to a target file.
The file ButtonDemo.java has 1578 bytes. Copy Done!
Download Code: Copy
Data streams are actually wrappers on existing input and output streams. They are inherited from the filter streams, which in facts are the wrappers. Ordinary input/output streams can work only with bytes. Filter streams gives the capability to work with integers, doubles, strings etc.
Exercise: Write a program that writes and reads from a binary file using data filter streams.
John 85.5 Jim 185.5 George 105.5
Download Code: Data Stream
FileInputStream/FileOutputStream is for reading and writing bytes from/to files. All the methods are inherited from InputStream and OutputStream respectively.
Exercise: Write a program that writes and reads from a binary file using input output streams
0 1 2 3 4 5 6 7 8 9
Download Code: File Stream
Exercise: Write a program that creates an applet which will show the national flag of a selected country and play its national anthem. The applet will automatically display the next country and play its national anthem once the previous national anthem audio clip is completely played.
Download Code: National Flats & National Anthems
Exercise: Write a program that creates an applet that has a bouncing ball. You can suspend/resume the ball using the buttons and also change the speed of the ball using the scroll bar.
Download Code: Bouncing Ball Applet
Exercise: Write a program that creates an applet for playing tic tac toe game between two players.
Download Code: Tic Tac Toe Applet
Exercise: Write a program that creates an applet for computing loan re-payment.
Download Code: Loan Applet
Exercise: Write a program that creates a simple Applet that displays a message. Use AppletViewer to run it as a standalone window.
Download Code: Simple Applet
Exercise: Write a program that has a text area and a button where the user can enter a message in the text area. Clicking the button should open a new window which has a histogram on the count of each letter in the text area message.
Download Code: Histogram
Exercise: Write a program that creates a message in a panel. The message can be moved across the panel using a vertical and a horizontal slider (instead of scroll bar which was used in exercise# 81).
Download Code: Slider Demo
Exercise: Write a program that creates a message in a panel. The message can be moved across the panel using a vertical and a horizontal scroll bar.
Download Code: Scroll Bar Demo
Exercise: Write a program that uses a drop down list from which the user can select one or more countries. The program will then populate the flags of respective countries in the panel.
Download Code: List Demo
Exercise: Write a program that enhances exercise 77 with a combo box from which the country can be selected to display its corresponding flag and flag description.
Download Code: Combo Box Demo
Exercise: Write a program that creates the following GUI which uses a non-editable text area.
Download Code: Text Area Demo
Exercise: Write a program on top of Exercise 75, where a text field is used to create the displayed message.
Download Code: Text Field Demo
Exercise: Write a program on top of Exercise 74, where radio buttons are used to give color to the message.
Download Code: Radio Button Demo
Exercise: Write a program on top of Exercise 73, where check boxes are added to center, bold and italic the message
Download Code: Check Box Demo
Exercise: Write a program that creates a frame with a message panel and two buttons - Left and Right. Clicking on the buttons make the message to move in the respective directions.
Download Code: Button Demo
Exercise: Write a program that creates a frame with a button with icons. The icon will change when mouse rolls over and when clicked (as in the images below).
Download Code: Button Icons
Exercise: Write a program that creates a live analog clock that ticks every second.
Download Code: Live Clock
The javax.swing.Timer class is a source component that can trigger ActionEvent at a predetermined interval. Listeners to this class needs to implement ActionListener. Listener can be added in the constructor of the Timer class or more listeners can be added using the addActionListener method on the class. Also the delay/interval can be adjusted at a later point of time using the setDelay method. Timer is started using the start() and stopped using the stop methods.
Exercise: Write a program that demonstrates javax.swing.Timer class where a message moves across a panel at an interval of 1 second.
Download Code: Moving Message with Timer
This exercise is to demonstrate Key Event. Key events enables the use of keys to control and perform actions. A key event is fired whenever a key is pressed, released or typed on a component.
Exercise: Write a program prints the character key pressed on a panel and help move it using the arrow keys
Download Code: Key Event
This exercise is to demonstrate Mouse events. MouseEvent inherits InputEvent. There are two listener interfaces MouseListener and MouseMotionListener. This exercise is a demo on MouseMotionListener
Exercise: Write a program that drags a message with the mouse on a panel
Download Code: Mouse Drag Message
Any subclass of a Window class can fire window events: window opened, window closed, window closing, window activated, window deactivated, window iconified and window de-iconified. This program creates a frame that listens to the window event and displays the message.
Exercise: Write a program that demonstrates Window Events and Window Listener
Window Activated Window Opened Window Iconified Window Deactivated Window Deiconified Window Activated Window Deactivated Window Iconified
Download Code: Window Event Demo
Exercise: Write a program that uses two buttons to control the size of the circle drawn on the GUI.
Download Code: Control Ball
This exercise is to demonstrate simple Event handling in Java GUI. Buttons are source of ActionEvent. Clicking a button invokes the actionPerformed method on the registered listeners. In this implementation, it will invoke getActionCommand() which by default returns the label of the button. The program also uses the event.getWhen() to return the time in long when the event was generated
This implementation also uses an inner class to create listener instance.
Exercise: Write a program that creates two buttons and print event information when clicked!
The OK button is clicked at Mon Nov 26 05:52:43 IST 2012 The Cancel button is clicked at Mon Nov 26 05:52:46 IST 2012 The Cancel button is clicked at Mon Nov 26 05:52:47 IST 2012 The OK button is clicked at Mon Nov 26 05:52:49 IST 2012 The OK button is clicked at Mon Nov 26 06:01:12 IST 2012
Download Code: Event Demo
Image icons can be used to display image on labels and buttones. However, ImageIcon displays a fixed size image. We can use the Image class to display images in flexible sizes.
ImageObserver is an asynchronous update interface that receives notifications of image information as the image is constructed. The Component class implements ImageObserver and hence all GUI Components is an instance of ImageObserver. Graphic's drawImage can then be used to draw the image
Exercise: Write a program that draws the following image.
Download Code: Draw Image
This exercise is to develop a useful class that displays a message in the panel. The class enables user to set the location of the message, center the message and move the message with specified interval.
Exercise: Write a program that creates a message panel that helps user to center the message or even move it.
Download Code: Message Panel
This exercise is to learn to write a String on a panel while centering it. To do so, we need to use the FontMetrics class to measure the exact height and width of the String
Exercise: Write a program that writes a String centered on the panel.
Download Code: Center Message
Exercise: Write a program that creates the following GUI with a Polygon painted on the panel
Download Code: Drawing Polygon
Exercise: Write a program that creates the following GUI with arcs painted on the panel
Download Code: Drawing Arcs
This exercise is to learn to draw on panels using the paintComponent(Graphics) method of the component. This method is invoked evry time a component is displayed/redisplayed. The Graphics object is automatically created by the JVM for every visible GUI component and then passed to the paintComponent method.
Panels are invisible and are used as containers. They are used to create the required layout. Panels can also be used for drawing,
Exercise: Write a program that creates a GUI similar to the following on a Panel.
Download Code: Draw on Panel
Exercise: Write a program that creates the following GUI for added image icons
Download Code: Image Icon GUI
Java Panels can also be used as a sub-container where a panel can be added to another panel. This gives better control in developing more compex GUI frames.
Exercise: Write a program that creates a GUI similar to a Microwave Oven interface.
Download Code: Microwave Interface
The BorderLayout manager divides the window into five areas - East, West, South, North and Center. Components can be added to the container using BorderLayout by using add method with the index as parameter. Index is a constant from BorderLayout.EAST, BorderLayout.WEST, BorderLayout.SOUTH, BorderLayout.NORTH or BorderLayout.CENTER
The components are laid out according to their preferred sizes where they are placed. The North and South components can stretch horizontally, East and West can stretch vertically and Center can stretch bothways.
Exercise: Write a program that demonstrates BorderLayout.
Download Code: Border Layout
GridLayout manager arranges components in a matrix/grid formation with the specified number of rows and columns. The components are arranged in the container from left to right in the first row until all the columns are occupied. It then starts with the next row and so on.
With GridLayout, if you resize the frame, the layout remains unchanged.
Exercise: Write a program that demonstrates GridLayout.
Download Code: Grid Layout
Flow Layout is a simple layout manager in Java GUI. The components are arranged in the container from left to right (depending on the alignment configuration used) in the order in which they are used. When one row is filled, the other row gets started.
You can specify the alignement using the following 3 constants: FlowLayout.LEFT, FlowLayout.RIGHT or FlowLayout.CENTER. Re-arranging the size of the frame, will automatically re-arrange the layout of the components.
Exercise: Write a program that demonstrates Flow Layout.
Download Code: Flow Layout
The problem is to write a program that finds out the prime numbers greater than Long.MAX_VALUE
Exercise: Write a program that prints five prime numbers greater than Long.MAX_VALUE
The program was running for hours and hence could not determine the output. However, to ensure that the program is fine, I tested the program for lower values.
Download Code: Big Prime Numbers
If we need to compute very huge numbers or high-precision floating point values, we need to use BigInteger and BigDecimal classes in the java.math package. Both these classes are immutable and also implements Comparable interface. You can use add, subtract, multiple, reminder etc. methods to perform computations.
Exercise: Write a program that prints the value for 50!
50! is 30414093201713378043612608166064768844377641568960512000000000000
Download Code: Large Factorial
The problem is to write a generic method to sort an array of Comparable objects. The objects are sorted using the compareTo() method of the Comparable interface.
Exercise: Write a program that sorts any generic array of objects that implements Comparable interface
Sorted Integer Objects: 2 3 4 Sorted Double Objects: -22.1 1.4 3.4 Sorted Character Objects: J a r Sorted String Objects: Fred John Tom
Download Code: Generic Sort
The problem is to write a GUI with two buttons - OK and Cancel. The program will print that the user has clicked OK/Cancel button on console.
Exercise: Write a program that creates a Frame with OK and Cancel buttons. Program should print on the console which button the user clicked.
Clicked OK Button Clicked Cancel Button Clicked OK Button Clicked OK Button Clicked Cancel Button Clicked Cancel Button
Download Code: Click Buttons
The problem is to write a method that checks whether two strings are Anagrams.
Two words are anagrams if they contain the same letters in any order. For example, "silent" and "listen" are anagrams.
Exercise: Write a program that prompts the user to enter two strings and verify whether they are anagrams
Enter the first String: garden Enter the second String: ranged garden and ranged are anagrams Enter the first String: gardens Enter the second String: dangers gardens and dangers are anagrams
Download Code: Anagrams
The problem is to write a method that counts the number of digits in a String.
This implementation uses Character.isDigit() method to verify whether a character is a digit.
Exercise: Write a program that prompts the user to enter a String and then prints out the number of digits in the String.
Enter string: d#1@bcd23f1gb Number of digits is: 4
Download Code: Count Digits
Java provides indexOf method in the String class to check whether a String is a sub-string of another string. The problem is to implement such a function.
This implementation helped me to come to know about labeled break and continue in Java. Default break/continue (non-labeled) breaks or continue from the inner most for, switch, while, do-while statements. However labeled ones help to break from/continue with the outer statements.
Exercise: Write a program that prompts the user to enter two Strings and then verify whether the first String is a sub-string of the second.
Enter the first string: el Enter the second string: hello el is a substring of hello Enter the first string: hello Enter the second string: al No substring found
Download Code: Check Sub-String
Write a method that returns the common prefix for two strings. For example, the common prefix for "distance" and "disappoint" is "dis". If the strings don't have a common prefix, print there is no common prefix between them.
Exercise: Write a program that prompts the user to enter two strings and display their common prefix.
Enter first string: paddy Enter second string: wheat No common prefix! Enter first string: Display Enter second string: disappoint Common prefix is : dis
Download Code: Common Prefix
A stack is a data structure that holds objects in a last-in, first-out fashion.
A stack has many applications. Java Compiler uses a stack to process method invocations. When a method is invoked, its parameter and local variables are pushed to the stack. When the mentod calls another method, the new method's parameters and local variables are pushed into the stock. When the method finishes its work and return to the caller, its associated space is released.
Exercise: Write a program that implements a stack for storing integers. Stack should internally use an array to hold the elements.
Pushing: 0 1 2 3 4 5 6 7 8 9 Popping: 9 8 7 6 5 4 3 2 1 0
Download Code: Stack of Integers
This exercise is to write a program that chooses a file using the dialog box and then prints the content of the file. This program uses JFileChooser to create the dialog box for choosing file and Scanner class for printing the output
Exercise: Write a program that chooses a text file using dialog box and then prints the output
BODY {
font-family: Segoe UI;
font-size: 10pt;
color: 000000;
margin-left: 10 px;
margin-top: 15 px;
background-position: top left;
background-repeat: repeat;
}
Download Code: Choose and Read File
The problem is to write a program that replaces all occurrences of a String in the file. The program uses Scanner class to read from the file and PrintWriter to write to the file.
Exercise: Write a program that replaces all occurrences of a String in a file. Replace "world" with "universe".
####hello_world.txt### Hello world! Good Morning world! ###hello_universe.txt### Hello universe! Good Morning universe!
Download Code: Replace Text In File
The problem is to write a program that reads from a text file using Scanner.
Exercise: Write a program that reads from a text file.
First Name: John Middle Name: T Last Name: Smith: 90 First Name: Eric Middle Name: K Last Name: Jones: 50
Download Code: Read From Text File
The problem is to write a program that writes to a text file using PrintWriter.
Exercise: Write a program that writes to a text file.
Download Code: Write to Text File
The problem is to write a program that prompts the user to enter a string and counts the number of occurrences of each letter of the string regardless of the case.
The following are the steps involved.
Exercise: Write a program that implements the above to count each letter of a string
Enter string: ababax a appears 3 times b appears 2 times x appears 1 time
Download Code: Count Each Letter
A Palindrome is a string that reads the same when read forward or backward. Few examples are "Malayalam", "Dad" , "Mom".
The problem is to write a program that prompts the user to enter a string and then check whether it is a Palindrome or not. One intuitive solution to the problem is to compare the first and last characters of the string. If they are same, then compare the second and second-last and so on. This can continue until all characters are matched or until a mismatch is found
Exercise: Write a program that implements the above to check whether a String is a Palindrome
Enter a String: moon moon is not a Palindrome! Enter a String: malayalam malayalam is a Palindrome!
Download Code: Check Palindrome
This exercise is to write a program that grades multiple choice test. The focus of this program is to use multi-dimensional arrays
Exercise: Write a program the grades the multiple choice test as below.
Students' Answers to the Questions
0 1 2 3 4 5 6 7 8 9
Student 0 : A B A C C D E E A D
Student 1 : D B A B C A E E A D
Student 2 : E D D A C B E E A D
Student 3 : C B A E C D E E A D
Student 4 : A B D C C D E E A D
Student 5 : B B E C C D E E A D
Student 6 : B B A C C D E E A D
Student 7 : E B E C C D E E A D
Key to the Questions
0 1 2 3 4 5 6 7 8 9
Key: D B D C C D A E A D
########### OUTPUT #################
For student 0's correct count is 7
For student 1's correct count is 6
For student 2's correct count is 5
For student 3's correct count is 6
For student 4's correct count is 8
For student 5's correct count is 7
For student 6's correct count is 7
For student 7's correct count is 7
Download Code: Grade Exam
Insertion sort algorithm sorts a list of values by repeatedly inserting a new element into a sorted sublist until the whole list is sorted. Starting out, the sorted sublist is the list of size 1 which is the first element in the list. It then inserts the second element to the list by comparing with the element in the list and so on. For the thirde element, it compares the element with the sorted sub-list of size 2. It will move the larger elements to the right and insert the element in the appropriate position in the sub list. With each element being processed, the sublist size increments by one until all the elements are processed.
Exercise: Write an implementation for Insertion Sort.
Before sort: List is : [69, 4, 2, 10, 60, 50, 59, 11, 7, 70, 66, 79, 45 ] After sort: List is : [2, 4, 7, 10, 11, 45, 50, 59, 60, 66, 69, 70, 79 ]
Download Code: Insertion Sort
Selection sort finds the largest number in the list and places it last. It then finds the largest number from the remaining list and places it second last and so on.
Exercise: Write an implementation for Selection Sort.
Before sort: List is : [69, 4, 2, 10, 60, 50, 59, 11, 7, 70, 66, 79, 45 ] After sort: List is : [2, 4, 7, 10, 11, 45, 50, 59, 60, 66, 69, 70, 79 ]
Download Code: Selection Sort
Java JDK provides Binary Search. This program is to implement such a binary search.
Exercise: Write an implementation of binary search and test as below.
List is : [2, 4, 7, 10, 11, 45, 50, 59, 60, 66, 69, 70, 79 ] Binary Search of 2: 0 Binary Search of 11: 4 Binary Search of 12: -6 Binary Search of 1: -1 Binary Search of 3: -2
Download Code: Binary Search
This program is to count the occurrences of each letter in an array.
Exercise: Write a program that generates 100 random lower case letters and then count the occurrence of each letter.
The lowercase letters are: m w u e b l g r p z v f h e n l u t c t e d k j k i r p a x g f p m v m x u c y w f b l k l k m w v c b l k s q a z h f g e v e p m v t g l j k u r b z k g q i s o z x y d f c n j u r c y j a l g q p The occurrence of each letter are: 3 a 4 b 5 c 2 d 5 e 5 f 6 g 2 h 2 i 4 j 7 k 7 l 5 m 2 n 1 o 5 p 3 q 4 r 2 s 3 t 5 u 5 v 3 w 3 x 3 y 4 z
Download Code: Count Letters
This program is to read student scores and assign grades to each student
Exercise: Write a program that reads student scores, get the best score and then assign grade to each student using the following scheme:
Grade is A if score is >= best - 10;
Grade is B if score is >= best - 20;
Grade is C if score is >= best - 30;
Grade is D if score is >= best - 40;
Grade is F otherwise.
Enter the number of students: 4 Please enter a score: 40 Please enter a score: 50 Please enter a score: 60 Please enter a score: 70 Student 0 score is 40 and grade is C Student 1 score is 50 and grade is B Student 2 score is 60 and grade is A Student 3 score is 70 and grade is A
Download Code: Assign Grades
This program is to find the largest number in an array and then count its occurrences.
Exercise: Write a program that reads 6 integers from the user, then find the largest of them and count its occurrences.
Enter the number: 3 Enter the number: 5 Enter the number: 2 Enter the number: 5 Enter the number: 5 Enter the number: 4 The array is 5 2 5 5 4 The largest number is 5 The number of occurrence is 3
Download Code: Max and its Count
This program is to display the calendar for given month of the year.
Exercise: Write a program that prompts the user to enter the year and the month, and then displays the entire calendar for the month as shown below.
Enter year as int (eg: 2003): 2006
Enter month as int (eg: 1 for January): 6
June 2006
-----------------------------
Sun Mon Tue Wed Thu Fri Sat
1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30
Download Code: Print Calendar
This program is to print random characters
Exercise: Write a program that prints random characters.
Random Character: ? Random Lower Case Character: d Random Upper Case Character: M Random Upper Case Digit Character: 0
Download Code: Random Characters
This exercise is to use sentinel value using Dialog Box.
Exercise: Write a program that takes input from users using Dialog Box. The program takes input integers and then sum them up and display the sum value.
Download Code: Sentinel Value (Dialog Box)