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CSC 185

Lab - 8

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Lab Practice QuestionsEncryption and Decryption

1) Write a Java program to implement Caesar Cipher.This is a method to encrypt a given text and decrypt theencrypted text. Please read information on Caesar cipher at wikipedia.org. Example:Encryption: Key -3, For the input stringWelcome to the lab encrypted text iszhofrph wr wkh oae

Decryption: You could use Key = 3The above encrypted result should printWelcome to the lab as the decrypted result.

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Your program should consist of 2 methodsEncryptMessage() andDecryptMessage().

2) Write a Java program to implement simple bankoperations withdraw and deposit using Javaclasses. The withdraw operation withdraws amount

from the bank account. The deposit operationdeposits the amount user enters from the console.

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Java I/O Means Java Input and Output. It is provided by the java.io package. This package has

InputStream and OutputStream. InputStream is defined for reading the stream, byte

stream and array of byte stream. Many list of classes provided by java.io package. Please

look into other sample classes athttp://www.roseindia.net/java/example/java/io/Classes-

Interfaces.shtml Ex: BufferedInputStream, BufferedOutputStream,

FileReader, FileWrite, FileInputStream,FileOutputStream.

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Standard streams

Java supports 3 standard streams: Standard Input: System.in to read input from

keyboard. Standard Output: System.out to write output

to be displayed. Standard Error: System.err to write error

output to be displayed.

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Files

File is a sequence of characters whichresides on disk.

We next see how to read from and write toa file.

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Reading from a Filepublic class Main

{

public static void main(String[] args){

File myfile = new File("C:\\Documents and Settings\\Raghavendra

Achanta\\Desktop\\bankacct.txt"); try{

Scanner s = new Scanner(myfile);while(s.hasNextLine()){

String data = s.nextLine();System.out.println(data);

}}catch(FileNotFoundException e){ System.out.println("No file specified is found");}

}}

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Write to a Filepublic class Main

{

public static void main(String[] args){

File myfile = new File("C:\\Documents and Settings\\RaghavendraAchanta\\Desktop\\bankacct.txt");

try {Scanner s = new Scanner(myfile);FileWriter f = new FileWriter(myfile);System.out.println("I am trying to write");

f.write("hello csc 185"); f.close();System.out.println("Wrote!");

} catch (IOException ex) { System.out.println("IO exception here!");}}}You have to close the file after writing ! It is not necessary to close the file after reading.