JAVA

Main topics:

Checked Exceptions

Files I/O Exercise

This week we will be practicing using Checked exceptions and basic file I/O.

Getting Started

To start this exercise, you should:

1. Open eclipse and start a new Java project named Lab10

2. Add a Class (named Files) to this project, and copy the contents of the Files.java file provided into it.

Requirements

Files.java

A very simple driver class which you can use as a base. Currently the program asks its user for the name of a text file which will be created; have the contents of the array words copied into it; and then be closed. Notice that since the PrintWriter constructor call may throw a FileNotFoundException, which is a checked exception, we must use try - catch blocks appropriately here.

Your job is to:

1. add the necessary components to the program so that the the original text file will be re-opened - again for output writing; have the contents of the arraymoreWords appended to it; and then closed again.

2. add the necessary components to the program so that the the text file will be re-opened one last time - this time for input reading; have its contents read (line by line) and printed to the screen; and then closed for the last time.

Your finished program will run / produce output similar to:

Enter the file name for output: test.txt

Enter the file name to append to: test.txt

Enter the file name for input: test.txt

words[0] = hello

words[1] = world

words[2] = and

words[3] = stuff

moreWords[0] = the

moreWords[1] = end

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What I have so far

import java.util.Scanner;

import java.io.*;

public class Files

{

public static void main(String[] args)

{

String[] words = {"hello", "world", "and", "stuff"};

String[] moreWords = {"the", "end"};

Scanner stdIn = new Scanner(System.in);

PrintWriter fileOut;

String fileOutName;

try

{

System.out.print("Enter the file name for output: ");

fileOutName = stdIn.next();

fileOut = new PrintWriter(fileOutName);

for (int i = 0; i < words.length; ++i)

fileOut.println("words[" + i + "] = " + words[i]);

fileOut.close();

//append with Filewriter

System.out.print("Enter the file name to append to: ");

fileOutName = stdIn.next();

PrintWriter fileOut1 = new PrintWriter(new FileWriter(fileOutName,true));

for (int j = 0; j < moreWords.length; ++j)

fileOut.println("moreWords[" + j + "] = " + moreWords[j]);

//after appending, use scanner to read file

System.out.print("Enter the file name for input: ");

fileOutName = stdIn.next();

}

catch (IOException e)

{

System.out.println("File Error : " + e.getMessage());

}

}

}

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Files Code that was first given

import java.util.Scanner; import java.io.*;

public class Files { public static void main(String[] args) { String[] words = {"hello", "world", "and", "stuff"}; String[] moreWords = {"the", "end"}; Scanner stdIn = new Scanner(System.in); PrintWriter fileOut; String fileOutName; try { System.out.print("Enter the file name for output: "); fileOutName = stdIn.next(); fileOut = new PrintWriter(fileOutName); for (int i = 0; i < words.length; ++i) fileOut.println("words[" + i + "] = " + words[i]); fileOut.close(); } catch (FileNotFoundException e) { System.out.println("File Error : " + e.getMessage()); } } }