What is the need to override the equals and hashCode methods in Java

0 votes
How can I decide when to use equals() and hashCode() efficiently?
Jan 2, 2019 in Java by Sushmita
• 6,920 points
3,206 views

1 answer to this question.

0 votes

You must override hashCode() in every class that overrides equals(). Failure to do so will result in a violation of the general contract for Object.hashCode(), which will prevent your class from functioning properly in conjunction with all hash-based collections, including HashMap, HashSet, and Hashtable.

- from Effective Java, by Joshua Bloch

By defining equals() and hashCode(), you can improve the usability of your classes as keys in hash-based collections. As the API doc for hashCode explains: "This method is supported for the benefit of hashtables such as those provided by java.util.Hashtable."

answered Jan 2, 2019 by Daisy
• 8,140 points

Related Questions In Java

0 votes
1 answer

What is the difference == and equals() in Java?

Both the answers (Syntaxes) are correct. If ...READ MORE

answered Jun 5, 2018 in Java by Akrati
• 3,190 points
941 views
0 votes
2 answers

What is the difference between Set and List in java?

List is an ordered sequence of elements. ...READ MORE

answered Apr 26, 2018 in Java by Akrati
• 3,190 points
63,234 views
0 votes
1 answer

What is the simplest way to read JSON from a URL in java

Read json from url use url.openStream() and read contents ...READ MORE

answered Jun 13, 2018 in Java by samarth295
• 2,220 points
5,125 views
0 votes
1 answer

Why there is the need of getters and setters in java

In Java getters and setters are completely ...READ MORE

answered Jun 26, 2018 in Java by scarlett
• 1,290 points
1,913 views
0 votes
1 answer

What is the difference between Polymorphism, Overriding and Overloading?

As far as I know, the main ...READ MORE

answered Jun 19, 2018 in Java by scarlett
• 1,290 points
11,854 views
0 votes
1 answer

What issues should be considered when we are overriding equals and hashCode in Java?

equals() must define an equivalent relation and ...READ MORE

answered Jun 21, 2018 in Java by Sushmita
• 6,920 points
692 views
0 votes
1 answer

Overriding private or static method in Java

You cannot override a private or static ...READ MORE

answered Jul 31, 2018 in Java by code.reaper12
• 3,500 points
16,212 views
0 votes
1 answer

How can we override back button to act like home button?

Most of the time you need to ...READ MORE

answered Dec 14, 2018 in Java by Daisy
• 8,140 points
2,162 views
+1 vote
3 answers

What is the syntax to declare and initialize an array in java?

You can use this method: String[] strs = ...READ MORE

answered Jul 25, 2018 in Java by samarth295
• 2,220 points
3,438 views
0 votes
2 answers

What is the use of toString method in Java and how can I use it ?

Whenever you require to explore the constructor ...READ MORE

answered Aug 23, 2018 in Java by Daisy
• 8,140 points
4,047 views
webinar REGISTER FOR FREE WEBINAR X
REGISTER NOW
webinar_success Thank you for registering Join Edureka Meetup community for 100+ Free Webinars each month JOIN MEETUP GROUP