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what is the use of declaring constructor as private?
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Answer / ranganathkini
By declaring the class constructor as private, other classes
cannot create instances of the class.
This design is usually used in singleton patterns.
| Is This Answer Correct ? | 22 Yes | 2 No |
Answer / ranganathkini
By making all the constructors of a class private, you can
also prevent other class from extending the class without
marking the class final.
| Is This Answer Correct ? | 9 Yes | 6 No |
Answer / suganya
prevent to access by other class even sub class cant have
permission to create object of that base class.
| Is This Answer Correct ? | 3 Yes | 0 No |
Answer / ravikiran
In order to restrict the class to get subclassed
| Is This Answer Correct ? | 6 Yes | 6 No |
Answer / anshul
A private constructor is a special instance constructor. It is commonly used in classes that contain static members only. If a class has one or more private constructors and no public constructors, then other classes (except nested classes) are not allowed to create instances of this class.
| Is This Answer Correct ? | 0 Yes | 1 No |
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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)
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