== (double equal operator)
|
.equals method
|
It
is an operator applicable for both primitives and object references.
|
It
is a method applicable only for object
references but not for primitives
|
In
the case of primitives == (double equal operator) meant for content
comparison, but in the case of object references == operator meant for
reference comparison.
|
By default .equals() method present
in object class is also meant for reference comparison.
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We
can't override== operator for content comparison in object references.
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We
can override .equals() method for content comparison.
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If
there is no relationship between argument types then we will get compile time error saying
incompatible types.(relation means child to parent or parent to child or same
type)
|
If there is no relationship between
argument types then .equals() method simply returns false and we won't get
any compile time error and runtime
error.
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For
any object reference r, r==null is always false.
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For
any object reference r, r.equals(null) is also returns false.
|
Relationship
between .equals() method and ==(double equal operator)
1.
If r1==r2
is true then r1.equals(r2)
is always true i.e., if two objects are equal by== operator then these objects are always equal by .equals( )
method also.
2.
If r1.equals(r2)
is false then r1==r2
is always false.
3.
If r1==r2
is false then we can't
conclude anything about r1.equals(r2) it may return true (or) false.
4.
If r1.equals(r2)
is true then we can't
conclude anything about r1==r2 it may returns true (or) false.
