The String class overrides the equals method it inherited from the Object class and implements logic to compare the two String objects character-by-character. The reason the equals method in the Object class refers to equality is because it doesn’t know how to do anything else.

Similarly, people ask why we override the equals method need?

If you just override the equal method, a. equals(b) is true, this means that the hash code of a and b must be equal, but need not occur. Note: The Object class’s hashCode() method always returns a new HashCode for each object. So if you need to use your object in the hashing-based collection, you need to override both equals() and hashCode().

Also, what is the meaning of the hashCode() and equals() methods? Using the hashCode() and equals() methods

equals(Object otherObject) – As the method name suggests, it is used to simply check the equality of two objects. The default implementation simply checks the object references of two objects to confirm their equality.

Accordingly, how does one override the equals method?

Therefore, the overridden equals() method must have the following Properties:

  1. Reflective: x. equals(x) is true .
  2. Symmetrical: x. equals(y) is true if and only if y. is equal to(x) .
  3. Transitive: if x. equal(y) and y. equals(z) are true, then so is x. equals(z) .

What happens if we just override equals?

Only Override HashCode, use the default Equals: Only the references to the same object will return true. In other words, the objects that you expected to be equal will not be equal when you call the equals method. Only override Equals, use the default HashCode: there may be duplicates in HashMap or HashSet.

How do you override a method in Java?

Method overriding rules:

  1. In Java, a method can only be written in subclass, not in the same class.
  2. The argument list should be exactly the same as that of the overridden method.
  3. The The return type should be the same or a subtype of the return type declared in the original overridden method in the superclass.

How to override hashCode and the equals method?

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

Can we override object class methods?

Object , hereafter simply referred to as Object, as the base class. Because of this, all Java classes inherit methods from Object . Half of these methods are final and cannot be overridden. However, the other methods in Object can and do override, often incorrectly.

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

Case 1: Both override equals (Object) and hashCode() methods. Whenever it(hashcode) is called more than once on the same object during execution of a Java application, the hashCode method must consistently return the same integer, provided , no Information used in equality comparisons on the object is changed.

What is the difference between == and equality?

In general, both the equality and the “==” operator in Java is used to compare objects to check equality, but here are some of the differences between the two: In simple terms, == checks if both objects point to the same location, whereas . equals() evaluates to compare values in the objects.

How to implement equal?


  1. Be sure to override equals(Object), so our method is always called.
  2. Include self and null checking for early return in simple edge cases.
  3. Use getClass to allow subtypes to have their own implementation (but no comparison between subtypes) or use instanceof and make equal to final (and subtypes can be equal).

How do I override the ToString method?

To override the ToString method in your class or struct:

  1. Declare a ToString method with the following modifiers and return type: C# Copy.
  2. Implement the method like this that it returns a string. The following example returns the name of the class in addition to data specific to a given instance of the class.

Can two objects that are not equal have the same HashCode to have?

Can two objects that are not equal have the same hash code? YES, two objects that are not equal to the equals() method can still return the same HashCode. BTW, this is one of the confusing bits of equals and hash code contracts.

What is the use of equals method in Java?

The equals() method compares two objects equality and returns true if they are equal. The equals() method provided in the Object class uses the identity operator (==) to determine whether two objects are equal. For primitive data types, this gives the correct result.

What happens if you don’t override the equals () method in the object class?

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

Can we just override hashCode without equals?

In fact, it’s worse because Many different books can have the same hash code. Yes, it is possible to just override hashCode() without violating its contract. Yes, it is also possible to just override equals() without violating the contract.

What is the hashCode method used for in Java?

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

How do you write not equal in Java?

To answer your question briefly, the ‘not equal’ sign in Java is the != operator. When working with non-primitive types like ‘String’, it is often preferable to use the type’s corresponding equals() instance method.

How do you compare two different objects?

If The two objects have the same values, equals() returns true. In the second comparison, equals() checks whether the passed object is null or whether it is typed as another class. If it’s a different class, the objects aren’t the same. Finally, equals() compares the fields of the objects.

What is polymorphism in Java?

Polymorphism in Java is a concept that allows us to perform a single action in different ways. We can do polymorphism in Java through method overloading and method overriding. When you overload a static method in Java, this is the example of compile-time polymorphism. Here we focus on runtime polymorphism in Java.

In Java, can we override just the equals method?

Override just equals() without overriding hashCode(). Because the default hashCode implementation in the object class returns different integers for different objects, e1 will be placed in one bucket and e2 will be placed in a different bucket than e1 if only the equals() method is overridden. hashCode() != e1.

What happens if we just override equals and not hashCode?

If we just override equals() and not hashCode(), the class uses its superclass implementation. So if two objects have the same data, equals() will return true, but hashCode() will return different values (two different address locations.