A method used in Java Objects and Java String. Used to check equivalence of:
- All fields
- Class type
stringa.equals(stringb)
Returns a Boolean
Overwritten Equals
Must satisfy the axioms of Equivalence:
- Reflexivity : For any non-null object,
x.equals(x)is true - Symmetric : For non-null objects
x.equals(y)y.equals(x) - Transitive : For non-null objects,
x.equals(y)y.equals(z)x.equals(z) - Consistent : For non-null objects, Multiple calls of
x.equals(y)must return the same output
Example
// Overriding equals() to compare two Complex objects
@Override
public boolean equals(Object o) {
// If the object is compared with itself then return true
if (o == this) {
return true;
}
/* Check if o is an instance of Complex or not
"null instanceof [type]" also returns false */
if (!(o instanceof Complex)) {
return false;
}
// typecast o to Complex so that we can compare data members
Complex c = (Complex) o;
// Compare the data members and return accordingly
return Double.compare(re, c.re) == 0
&& Double.compare(im, c.im) == 0;
}