Pallavi Chakraborty

Hello everybody,
I have an application which takes the SSN of the user you want to delete.
It goes through the lines and if it finds the SSN it should not write it to a file.
public void deleteEmployee(int SSN)throws IOException { try { FileReader fr = new FileReader("EmpDetails.txt"); //creating a File Reader Object BufferedReader br = new BufferedReader(fr); String contents = ""; String read = ""; while(br.ready())//Tells whether this stream is ready to be read. { contents = br.readLine(); StringTokenizer st = new StringTokenizer(contents, ":");//creating a System Tokenizer. int SSn = Integer.parseInt(st.nextToken());//get the SSn part //System.out.print(SSn); if(!(SSn == SSN))//CHECK IF THE SSN ENTERED IS IN THE FILE { String firstname = st.nextToken();//get the firstname part String lastname = st.nextToken();//get the lastname part delcontents = SSn + " " + firstname + " " +lastname + " "; //FileWriter fw1 = new FileWriter("EmpDetails.txt"); //PrintWriter pw1 = new PrintWriter(fw1, true); //System.out.print(SSN); //String firstname = st.nextToken();//get the firstname part //String lastname = st.nextToken();//get the lastname part //pw1.flush();//Flush the stream. //If the stream has saved any characters from the various write() methods //in a buffer, write them immediately to their intended destination. //Then, if that destination is another character or byte stream, flush it. //Thus one flush() invocation will flush all the buffers in a chain of Writers and OutputStreams. //pw1.print(SSn); //pw1.print(":"); //pw1.print(firstname); //pw1.print(":"); //pw1.print(lastname); //pw1.print(""); //pw1.close(); } } System.out.print(delcontents); } catch(Exception e) { System.out.print("Error now"); } }
I have thought a lot but I am not getting it right.
Thanks
Pallavi

Hello Gayathri,
It worked when I chenged the code to
while(br.ready()
{
//code
}
Can you guide me towards how we can delete a record.
Thanks
Pallavi

Hello Gaya,
i tried changing the loop from a do-while to a while. I am still getting the error.
May be I am doing something wrong.
Thanks
Pallavi

Hello everybody,
I have an application here which takes the choice from a user and does the necessary processing. I am using text files for this.
The following are the three programs:
1. Employee1.java
2. Employee1App.java
3. Employee2.java
I had a couple of doubts:
1.
Employee1App has the main method. Choice3 takes us to Employee2 file which checks if an employee exists. the program is working but it is also printing the catch part of the try-catch statement even after it has successfully executed the try part.
2.
Is there a way to delete a record ..... just like we have readLine() is there a way tp delete a line.

Thank you very much.
Pallavi

import java.io.FileWriter; import java.io.PrintWriter; import java.io.*; public class Employee1 { private int SSNumber = 0; private String firstname = ""; private String lastname = ""; public Employee1(int SSN, String fname, String lname) { SSNumber = SSN; firstname = fname; lastname = lname; try { addEmployee1(SSNumber,firstname,lastname); } catch(IOException e) { } }//end of Employee1 constructor . public void addEmployee1(int s, String f, String l) throws IOException { try { FileWriter fr = new FileWriter("EmpDetails.txt", true); PrintWriter pw = new PrintWriter(fr); //pw.print("Getting ready to flush the data"); pw.flush(); //pw.println("SSN " + "FirstName " + "LastName"); //pw.println(""); pw.print(s); pw.print(":"); pw.print(f); pw.print(":"); pw.print(l); pw.println(""); pw.close(); } catch(Exception e) { } }//end of method addEmployee1 }
import javax.swing.JOptionPane; import java.io.*; public class Employee1App { public static void main(String args[]) { String message = "Please choose what you want to do ? +\n" + "1 - Add a new employee\n\n" + "2 - Check if a file exists\n\n" + "3 - Look up an existing employees details\n\n" + "4 - Quit"; String option = JOptionPane.showInputDialog(message); int optionint = Integer.parseInt(option); switch(optionint) { case 1:// the user enters 1 String a = JOptionPane.showInputDialog("Enter your SSN:"); if(a.length() < 9) { System.out.print("The SSN should be 9 digits long"); a = JOptionPane.showInputDialog("Enter your SSN:"); } int SSNumber = Integer.parseInt(a); String b = JOptionPane.showInputDialog("Enter your first name:"); String c = JOptionPane.showInputDialog("Enter your last name:"); new Employee1(SSNumber, b, c); System.out.print("Hi"); break; case 2:// the user enters 2 String e = JOptionPane.showInputDialog("Please enter the filename"); File data = new File("EmpDetails.txt"); if(data.exists()) { Employee2 e2 = new Employee2(); e2.searchEmployee(); } else { e = JOptionPane.showInputDialog("File does not exist. Please enter the correct filename"); } System.out.print("Hiiiiii"); break; case 3: //the user emters 3 String j = JOptionPane.showInputDialog("Enter the SSN of the employee"); if(j.length() < 9) { System.out.print("The SSN should be 9 digits long"); j = JOptionPane.showInputDialog("Enter your SSN:"); } int SSN1 = Integer.parseInt(j); new Employee2(SSN1); break; case 4: System.exit(0); break; } } }

import java.io.FileReader; import java.io.BufferedReader; import java.io.*; import java.util.StringTokenizer; import javax.swing.JOptionPane; public class Employee2 { private int SocSecNumber; public Employee2(int SSNumber)//CONSTRUCTOR WHICH TAKES AN INTEGER AS INPUT { SocSecNumber = SSNumber;System.out.print(SocSecNumber); try { validateEmployee(SocSecNumber); } catch(IOException e) { } } public void validateEmployee(int SSN) throws IOException { try { FileReader fr = new FileReader("EmpDetails.txt"); //creating a File Reader Object BufferedReader br = new BufferedReader(fr); String contents; do { contents = br.readLine(); StringTokenizer st = new StringTokenizer(contents, ":");//creating a System Tokenizer. int SSn = Integer.parseInt(st.nextToken());//get the SSn part if(SSn == SocSecNumber)//CHECK IF THE SSN ENTERED IS IN THE FILE { System.out.print("Match Found"); String firstname = st.nextToken();//get the firstname part String lastname = st.nextToken();//get the lastname part System.out.println("SSN: " + SSn + " " + "Fname: " + firstname + " " + "Lname: " + lastname); } }while(contents != null); } catch(Exception e) { System.out.print("Error now"); } }//END OF METHOD VALIDATE EMPLOYEE }//END OF CLASS EMPLOYEE2

Hello everybody,
I have an application which has two parts. It gets employee data from the user, SSN, firstname, lastname and stores it in a text file.
This data is stored in the format:
SSN: FirstName: LastName.
Then the String Tokenizer needs to get the individual parts of this using the delimiter:.
I am pasting the three files.
1.Employee1 - writes to the file
2.Employee App - calls Employee1
3.Employee2 - reads from file
The reading part using the String Tokenizer is not working. It is directly going to the catch statement.
I will really appreciate it if you can help me with this.
import java.io.FileWriter; import java.io.PrintWriter; import java.io.*; public class Employee1 { public Employee1(int SSN, String fname, String lname) { try { addEmployee1(SSN,fname,lname); } catch(IOException e) { } }//end of Employee1 constructor . public void addEmployee1(int SSNumber, String firstname, String lastname) throws IOException { try { FileWriter fr = new FileWriter("EmpDetails.txt", true); PrintWriter pw = new PrintWriter(fr); //pw.print("Getting ready to flush the data"); pw.flush(); //pw.println("SSN " + "FirstName " + "LastName"); //pw.println(""); pw.print(SSNumber); pw.print(":"); pw.print(firstname); pw.print(":"); pw.print(lastname); pw.close(); } catch(Exception e) { } }//end of class Employee1 }
import javax.swing.JOptionPane; public class Employee1App { public static void main(String args[]) { String a = JOptionPane.showInputDialog("Enter your SSN:"); String b = JOptionPane.showInputDialog("Enter your first name:"); String c = JOptionPane.showInputDialog("Enter your last name:"); int SSNumber = Integer.parseInt(a); new Employee1(SSNumber, b, c); } }
import java.io.FileReader; import java.io.BufferedReader; import java.util.StringTokenizer; public class Employee2 { public static void main(String args[]) throws IOException { try { FileReader fr = new FileReader("filename.txt"); //creating a File Reader Object BufferedReader br = new BufferedReader(fr); while(br.ready()) { String line = br.readLine(); StringTokenizer st = new StringTokenizer(line, ":");//creating a System Tokenizer. int SSn = Integer.parseInt(st.nextToken());//get the SSn part String firstname = st.nextToken();//get the firstname part String lastname = st.nextToken();//get the lastname part System.out.print("SSN" + SSn + "Fname" + firstname + "Lname" + lastname);//Print out all } br.close(); } catch(Exception e) { System.out.print("Error now"); } } }

Thanks
Pallavi

Thanks a lot,
Will choose a better topic next time>
Pallavi

Hello everybody,
I have two programs. One gets the first and last name from the user and sends them to a File.
Another program tries to read this first name and
last name from the file.
However, I have seen that nothing is getting written on to the file.
I am pasting the code for the two programs.
public class Test1 { public static void main(String args[]) { Employee employee; String output = ""; String a = JOptionPane.showInputDialog("Enter your first name"); String c = JOptionPane.showInputDialog("Enter your last name"); Boss b = new Boss(a, c, 800.0); try { FileWriter fw = new FileWriter("filename.txt", true); PrintWriter pw = new PrintWriter(fw); pw.print(a); pw.print(c); } catch(Exception e) { System.out.print("File Error"); } DecimalFormat precision2 = new DecimalFormat("0.00"); employee = b; output += employee.toString() + "earned $" + precision2.format(employee.earnings()); JOptionPane.showMessageDialog(null, output, "Demonstrating Polymorphism", JOptionPane.INFORMATION_MESSAGE); System.exit( 0 ); } }
Here is the second code
import java.io.FileReader; import java.io.BufferedReader; public class EmployeeReader { public static void main(String args[]) { try { FileReader fr = new FileReader("filename.txt"); BufferedReader br = new BufferedReader(fr); // reads in the next line from the file String lineOne = br.readLine(); System.out.print(lineOne); } catch(Exception e) { System.out.print("Error now"); } } }
Please help me out.
Pallavi

Hello Jim,
I tried again and this code compiles without error:
import javax.swing.JOptionPane; //I added this piece of code to import java.net.URL; import java.net.MalformedURLException; import java.net.URL; //class MalformedURLException extends Exception { // MalformedURLException(String msg) //{ // super(msg); //} //} public class ThrowEx { public void urltest() { String url = JOptionPane.showInputDialog("Enter an URL"); MalformedURLException oops = null; URL u; if(!(url == null)) { try { u = new URL(url); System.out.print(u); } catch(MalformedURLException e) { System.out.print("Dealt with:" + e); } } } public static void main(String args[]) { new ThrowEx().urltest(); System.out.println("returning from main"); } }
What do you think ?
Pallavi

Hello Jim,
I worked on it a little more and came up with this:
public void urltest() { String url = JOptionPane.showInputDialog("Enter an URL"); MalformedURLException oops = null; URL u =null; if(!(url == null)) { try { u = new URL(url); System.out.print(u); } catch(MalformedURLException e) { System.out.print("Dealt with:" + e); } }
However I get these two errors:
C:\Pallavi's\Javah\JCreator LE\MyProjects\Test1\Ex5.7\ThrowEx.java:27: unreported exception java.net.MalformedURLException; must be caught or declared to be thrown
u = new URL(url);
^
C:\Pallavi's\Javah\JCreator LE\MyProjects\Test1\Ex5.7\ThrowEx.java:30: exception MalformedURLException is never thrown in body of corresponding try statement
catch(MalformedURLException e)
^
2 errors
Process completed.
Thanks
Pallavi

Hello Jim,

The if statement is for an unknown protocol.
I tried the follwong code but I am still not clear.
try { // I added this code which creates an object of the class URL passing a string as a parameter. URL u = new URL(url); if(u == null) throw new MalformedURLException("test"); else System.out.print(u); } catch (MalformedURLException e) { System.out.println("Dealt with: " + e); }
The if part , how do we specify the unknown protocol.
The only thing I could think of is the URL being a null.
I appreciste your patience on this.
Thank you
Pallavi

Hi Jim,
This line is supposed to create an object of class URL and send a string object into its constructor.If the string specifies an unknown protocol, then an exception will be thrown.
I know to catch the Malformed URL exception, it has to reported somewhere. I had tried moving the throw statement to the method urltest and making it a throws statement.
I think I am missing a very simple point.
I just don't know what.
Thanks
Pallavi

Hello Barry,
I tried adding the constructor of java.net.URL
I am pasting the modified code.

import javax.swing.JOptionPane; //I added this piece of code to import java.net.URL; import java.net.URL; class MalformedURLException extends Exception { MalformedURLException(String msg) { super(msg); } } public class ThrowEx { public void urltest() { String url = JOptionPane.showInputDialog("Enter an URL"); try { // I added this code which creates an object of the class URL passing a string as a parameter. URL u = new URL(url) throw new MalformedURLException("test"); } catch (MalformedURLException e) { System.out.println("Dealt with: " + e); } } public static void main(String args[]) { new ThrowEx().urltest(); System.out.println("returning from main"); } }
However, I get this error:
[CODE}
C:\JCreator LE\MyProjects\Test1\Ex5.7\ThrowEx.java:22: ';' expected
URL u = new URL(url) throw new MalformedURLException("test");
^
[/CODE]
Thank you
Pallavi

Let me try that,
Pallavi

Hello everybody,
I have the following program which catches a MalformedURLException. The value of the string variable URL is initialized to null.
Instead of this, can I get the URL as an input from the user and then check to see if it is in the URL format.
I am not sure how this would be done.
Here is the code
import javax.swing.JOptionPane; class MalformedURLException extends Exception { MalformedURLException(String msg) { super(msg); } } public class ThrowEx { public void urltest() { try { String url = null; if(url == null) { throw new MalformedURLException("test"); } } catch (MalformedURLException e) { System.out.println("Dealt with: " + e); } } public static void main(String args[]) { new ThrowEx().urltest(); System.out.println("returning from main"); } } Thanks in advance Pallavi

Hi Rene and Mark,
The first time I followed the steps : I got a folder in my directory which had the name - META-INF/MANIFEST.MF
But since then i do not actually get a manifest file.
Can that be the reason.
Thank you
Pallavi