Answer Posted / ashokmail

we can check the null status of the object for it is
exits or not.

For Example
class java{
public java(){
}
}

class javause{
private java j;
public javause(){
if ( j != null)
j = new java();
}
public static void main(String args[]){
new javause();
}
}

How many types of interfaces are there?

1142

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Why does java not allow multiple public classes in a java file ?

4657

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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)

1988

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Is the empty set a singleton?

1026

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What is lossy conversion in java?

1277

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Is it possible for a yielded thread to get chance for its execution again?

993

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How do I get the | symbol on my keyboard?

1122

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how can i use a nonsynchronized hashtable?

2623

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What is meant by polymorphism?

1071

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What is array size in java?

1018

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What is numeric data type?

1043

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What is the use of default method in interface in java? Explain

1046

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What is method reference in java?

1194

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What is public/private protected in java?

1083

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Is there any way to skip finally block of exception even if some exception occurs in the exception block?

1115

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