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equals() is a method defined in the Object class thus the default implementation of the . equals() method compares the object references or the memory location where the objects are stored in the heap. Thus by default the . equals() method checks the object by using the “==” operator.
In the first comparison, equals() compares the current object instance with the object that has been passed. If the two objects have the same values, equals() will return true . In the second comparison, equals() checks to see whether the passed object is null, or if it's typed as a different class.
Uses of hashCode() and equals() Methods Its default implementation simply checks the object references of two objects to verify their equality. By default, two objects are equal if and only if they are refer to the same memory location. Most Java classes override this method to provide their own comparison logic.
The equals() and hashcode() are the two important methods provided by the Object class for comparing objects. Since the Object class is the parent class for all Java objects, hence all objects inherit the default implementation of these two methods.
Yes, the default implementation is Object's (generally speaking; if you inherit from a class that redefined equals and/or hashCode, then you'll use that implementation instead).
From the documentation:
equals
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).
hashCode
As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the JavaTM programming language.)
From Object in one of the JVM implementations:
public boolean equals(Object object) {
return this == object;
}
public int hashCode() {
return VMMemoryManager.getIdentityHashCode(this);
}
In both cases it's just comparing the memory addresses of the objects in question.
There are default implementations of equals() and hashCode() in Object. If you don't provide your own implementation, those will be used. For equals(), this means an == comparison: the objects will only be equal if they are exactly the same object. For hashCode(), the Javadoc has a good explanation.
For more information, see Effective Java, Chapter 3 (pdf), item 8.
Yes, from Object class since your class extends Object implicitly. equals simply returns this == obj. hashCode implementation is native. Just a guess - it returns the pointer to the object.
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