why HashTable not allow null key and value

2 Answers   Crimson Logic,

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Can a constructor call the constructor of parent class?

0 Answers  

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int a=10,b=20,c=30 a= b+c;b=a+c;c=a+b; System.out.println("The value is"+a+b+c;

17 Answers   Honeywell,

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explain the concept of inheritance with an example?

9 Answers   Polaris,

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I/O blocking means?

1 Answers  

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Define iterator and methods in iterator?

0 Answers  

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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)

0 Answers  

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How does the garbage collector works in java?

0 Answers   Cyient,

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Can a class have multiple superclasses?

0 Answers  

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When object is created and destroyed?

0 Answers  

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Difference between Map & Hashmap

2 Answers   Mastek,

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JSP is by default thread safe or not? what is the meaning of isThreadSafe="true" and isThreadSafe="false". Explain it? Thanks, Seenu

9 Answers   Huawei,

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