Why we override equals() method? It needs to be overridden if we want to check the objects based on the property. For example, we want to check the equality of employee object by the id. Then, we need to override the equals() method.

What is the purpose of the equals () method?

The equals() method compares two strings, and returns true if the strings are equal, and false if not.

Why overriding hashCode and equals method?

In order to use our own class objects as keys in collections like HashMap, Hashtable etc.. , we should override both methods ( hashCode() and equals() ) by having an awareness on internal working of collection. Otherwise, it leads to wrong results which we are not expected.

What is the use of overriding equals method in Java?

All classes in Java inherit from the Object class, directly or indirectly (See point 1 of this). The Object class has some basic methods like clone(), toString(), equals(),.. etc. We can override the equals method in our class to check whether two objects have same data or not.

What equals () method must you override?

You must have to override both equals() and hashCode() method in Java , otherwise your value object will not be able to use as key object in HashMap because working of HashMap is based on equals() and hashCode to read more see , How HashMap works in Java.

What happens if we do not override hashCode () and equals () in HashMap?

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.

What happens if we do not override equals?

We know that two objects are considered equal only if their references point to the same object, and unless we override equals and hashCode methods, the class object will not behave properly on hash-based collections like HashMap , HashSet , and Hashtable .

Can you override equals method?

You can override the equals method on a record, if you want a behavior other than the default. But if you do override equals , be sure to override hashCode for consistent logic, as you would for a conventional Java class.

Why is it important to write the equals () method when writing a class?

The reason the equals method in the Object class does reference equality is because it does not know how to do anything else. Remember, every class in Java is an Object (via inheritance).

Can we override equals method in class?

Can we override the equals() method in Java? To compare two objects the object class provides a method with name equals(), this method accepts an object and compares it with the current object. If the references of these two objects are equal, then it returns true else this method returns false.

What will happen if you compare two objects without overriding equals ()?

Though the values of dog1 and dog2 are the same, equals() method always checks the reference of the two objects i.e if both the objects passed refer to the same object or not and not their values. Therefore, it is advisable not to use this method in comparing objects without overriding it.

Which class does not override the equals () and hashCode () methods?

StringBuilder/ StringBuffer does not override equals() and hashCode() method.

Where can we use == and equals () Write suitable example?

We can use == operators for reference comparison (address comparison) and . equals() method for content comparison.
equals method to check whether two objects contain the same data or not.

  • In the above example, we create 3 Thread objects and 2 String objects.
  • In the first comparison, we check whether t1 == t3 or not.

What is the difference between == and equals () method?

equals() method. The major difference between the == operator and . equals() method is that one is an operator, and the other is the method. Both these == operators and equals() are used to compare objects to mark equality.

What is the difference between equals () method and double equal operator in Java?

== should be used during reference comparison. == checks if both references points to same location or not. equals() method should be used for content comparison. equals() method evaluates the content to check the equality.

What is difference between operator and equals () method explain with example?

“==” operator compares the objects based on their location in the memory. The default version of equals() method also does the same thing as “==” operator. But, equals() method is meant to be used for comparison of two objects based on their contents. For that you have to override the equals() method.

What is difference between equals () and compareTo () method?

equals() checks if two objects are the same or not and returns a boolean. compareTo() (from interface Comparable) returns an integer. It checks which of the two objects is “less than”, “equal to” or “greater than” the other. Not all objects can be logically ordered, so a compareTo() method doesn’t always make sense.

What is equals method in object class Java?

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

What is difference between equals method of object class and string class?

The equals() method of the String class is not same as the equals() method of the Object class. It is overridden, this method accepts a String value and compares it with the current object and returns true only if the character sequences in the both String objects are exactly same.

When you compare strings with the equals () method you are comparing their values not their memory addresses?

When you compare Strings with the == operator, you are comparing their values, not their memory addresses. When you must determine whether a String is empty, it is more efficient to compare its length to 0 than it is to use the equals () method.

What is the difference between equality operator and equals () method in C #?

The Equality Operator ( ==) is the comparison operator and the Equals() method compares the contents of a string. The == Operator compares the reference identity while the Equals() method compares only contents.

What is the difference between == and === in Java?

== in JavaScript is used for comparing two variables, but it ignores the datatype of variable. === is used for comparing two variables, but this operator also checks datatype and compares two values. Checks the equality of two operands without considering their type.

What is a singleton class in Java?

In Java, Singleton is a design pattern that ensures that a class can only have one object. To create a singleton class, a class must implement the following properties: Create a private constructor of the class to restrict object creation outside of the class.

Why are strings immutable in Java?

The String is immutable in Java because of the security, synchronization and concurrency, caching, and class loading. The reason of making string final is to destroy the immutability and to not allow others to extend it. The String objects are cached in the String pool, and it makes the String immutable.