What problems will occur when you don?t use layout managers?
178
The following program reads data (details of students) from
a file named students.txt and
converts it into e-mail addresses. The results are written
to a file named studentemail.txt.
students.txt consists of a number of lines, each containing
the data of a student in colon
delimited format:
Last Name:First Name:Student Number
Each input record is converted to an e-mail address and
written to studentemail.txt in the
following format:
the first character of the last name + the first character
of the first name + the last four digits of
the student number + “@myunisa.ac.za”
import java.io.*;
public class EmailConverter {
public static void main(String[] args) throws IOException {
BufferedReader input = new BufferedReader(new FileReader
("students.txt"));
PrintWriter output = new PrintWriter(new FileWriter
("studentemail.txt"));
String line = input.readLine();
while (line != null) {
// Extract the information for each student
String[] items = line.split(":");
// Generate the email address
String email = "" + items[0].charAt(0) + items[1].charAt(0)
+
items[2].substring(4,8) + "@myunisa.ac.za";
email = email.toLowerCase();
// Output
output.println(email);
line = input.readLine();
}
input.close();
output.close();
}
}
Rewrite the class so that it handles possible errors that
may occur. In particular, it should do the
following:
• It should catch at least three appropriate exceptions
that might occur, and display suitable
messages.
• At this stage, the program will not run correctly if
there is an empty line in the input file.
Change the program so that if an empty line is encountered,
an exception is thrown and the
empty line is ignored. This exception should be handled
with the display of a suitable error
message.
• Before the e-mail address is added to the output file,
check if the student number has 8
digits. If not, throw an InvalidFormatException (which the
program should not handle itself)
21
What is a resource leak ?
125
How can we handle runtime exceptions? write one sample
program? Can we write runtime exceptions beside the throws
key word? if yes write sample program?
How will you serialize a singleton class without violating
singleton pattern?
35
I need some details about an employee. i have only the
employee id in my presentation layer(JSP).I entered that ID
and click "Show Details" Button. Question is how the JSP
pass that id to Controller layer and DAO and what mechanism
we are using to retrive data from DB and how the data
passed to JSP as a Output. Please explain in detail.
How listener identify that the event came from a particular
object?
107
Q1.A. Write note on “The class path Environment Variable”?
B. Which are different kinds of source code?
Q2.A. How to create an interface?
B. Why convert an applet to an application?
Q3.A. How to use Media tracker Class.
B. How to use string tokenizer class.
Q4 A. Explain the overview of UDP messaging.
B. Difference between SQL Exception class and SQL
Warning class.
Q5. A. How to create com object in Java?
B. Write short notes on “The properties class”
Q6. A. When object is created and destroyed?
B. Explain the JDB in depth & command line.
C. Write short notes on Web Sites.
23. Storage space in java is of the form
Stack
Queue
Heap
List
24. What is java code embedded in a web page known as
Applets
Servlets
scriptlets
snippets
25. Which of the following attributes are compulsory with
an <applet> tag?.
code,height & width.
26. What does 'CODEBASE' in an applet tag specify?.
Files absolute path.
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