Interested to Buy Any Domain ? << Click Here >> for more details...
Why do we need to override equals() and hascode() method of object class?
- 1 Answers
- 3664 Views
- Cognizant, I also Faced
- E-Mail Answers
Answer Posted / javamasque
As per equality contract of Java if two objects are equal then they should return equal integer, means if obj1.equals(obj2) then obj1.hashCode() == obj2.hashCode();
As we override equals method we compares equality on value of each property inside 1st object with 2nd object, as it finds all properties are equal then returns true else false.
As we override hascode method we generate a unique integer by multiplying with prime number. If we multiply with prime number then there is most possibility to get unique integer. The prime number 31 is mostly used as the hascode method is override.
| Is This Answer Correct ? | 2 Yes | 0 No |
Post New Answer View All Answers
What does %4d mean in java?
What do you mean by object?
For class CFoo { }; what default methods will the compiler generate for you>?
What are packages in java?
What is Mutex (Mutual Exclusion Object) ?
Can final class have constructor?
Explain serialization and deserialization in java?
Can an interface have a constructor?
How many bits is a string in java?
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)
Can we convert integer to string in java?
Can we override static methods in java?
How can we create a thread in java?
What data type is a string?
What is immutable data?
