Where do we use hashCode and equals method in Java?

If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result. It is not required that if two objects are unequal according to the equals(java. lang.

What is the use of hashCode and equals method in Java?

The hashcode() method returns the same hash value when called on two objects, which are equal according to the equals() method. And if the objects are unequal, it usually returns different hash values.

Where do we use hashCode in Java?

hashCode() is used for bucketing in Hash implementations like HashMap , HashTable , HashSet , etc. The value received from hashCode() is used as the bucket number for storing elements of the set/map. This bucket number is the address of the element inside the set/map.

How hashCode () and equals () method are used in HashMap?

In HashMap, hashCode() is used to calculate the bucket and therefore calculate the index. equals method is used to check that 2 objects are equal or not. … HashMap uses equals() to compare the key whether the are equal or not. If equals() method return true, they are equal otherwise not equal.

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What is the use of equals method in Java?

The Java String class equals() method compares the two given strings based on the content of the string. If any character is not matched, it returns false. If all characters are matched, it returns true.

What is hashCode used for?

The purpose of the hashCode() method is to provide a numeric representation of an object’s contents so as to provide an alternate mechanism to loosely identify it. By default the hashCode() returns an integer that represents the internal memory address of the object.

What is the hashCode method?

The hashCode method is an inbuilt method that returns the integer hashed value of the input value. Here are a few key concepts to remember: Multiple invocations of the hashCode must return the same integer value within the execution of a program unless the Object used within the equals method changes.

What is hashCode and how it works?

Simply put, hashCode() returns an integer value, generated by a hashing algorithm. Objects that are equal (according to their equals()) must return the same hash code. Different objects do not need to return different hash codes.

Can 2 objects have same hashCode?

It is perfectly legal for two objects to have the same hashcode. If two objects are equal (using the equals() method) then they have the same hashcode. If two objects are not equal then they cannot have the same hashcode.

What are equals () and hashCode () overriding rules?

if a class overrides equals, it must override hashCode. when they are both overridden, equals and hashCode must use the same set of fields. if two objects are equal, then their hashCode values must be equal as well. if the object is immutable, then hashCode is a candidate for caching and lazy initialization.

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What happens if we don’t override hashCode method?

If you don’t override hashcode() then the default implementation in Object class will be used by collections. This implementation gives different values for different objects, even if they are equal according to the equals() method.

Why do we override 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.

How is hashCode calculated?

The String hashCode() method returns the hashcode value of this String as an Integer. If you will try to find the hashcode value of this string again, the result would be the same. …

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