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.
What happens if we override only equals?
If we only override equals(Object) method, when we call map. put(g1, “CSE”); it will hash to some bucket location and when we call map. put(g2, “IT”); it will hash to some other bucket location because of different hashcode value as hashCode() method has not been overridden.
What happens if we don’t override equals method?
Overriding only equals() method without overriding hashCode() causes the two equal instances to have unequal hash codes, which violates the hashCode contract (mentioned in Javadoc) that clearly says, if two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two …
What happens if we don’t override hashCode and equals?
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.
What equals method must you override?
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 equals () method must you override?
As a side note, when we override equals(), it is recommended to also override the hashCode() method. If we don’t do so, equal objects may get different hash-values; and hash based collections, including HashMap, HashSet, and Hashtable do not work properly (see this for more details).
Is it mandatory to override hashCode If you override equals method?
If you override the equals(), you MUST also override hashCode(). Otherwise, a violation of the general contract for Object. hashCode() will occur, which results unexpected behavior when your class is in conjunction with all hash-based collections.
What is equals and hashCode contract?
hashCode() and equals() contract The basic rule of the contract states that if two objects are equal to each other based on equals() method, then the hash code must be the same, but if the hash code is the same, then equals() can return false.
Is it mandatory to override hashCode and equals method?
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 are the important things to consider when implementing equals method?
The equals() method must be:
- reflexive: an object must equal itself.
- symmetric: x. equals(y) must return the same result as y. equals(x)
- transitive: if x. equals(y) and y.
- consistent: the value of equals() should change only if a property that is contained in equals() changes (no randomness allowed)