equals
public boolean equals (Object o)
Indicates whether some other object is "equal to" this one.
The equals method implements an equivalence relation
on non-null object references:
- It is reflexive: for any non-null reference value
x, x.equals(x) should return
true.
- It is symmetric: for any non-null reference values
x and y, x.equals(y)
should return true if and only if
y.equals(x) returns true.
- It is transitive: for any non-null reference values
x, y, and z, if
x.equals(y) returns true and
y.equals(z) returns true, then
x.equals(z) should return true.
- It is consistent: for any non-null reference values
x and y, multiple invocations of
x.equals(y) consistently return true
or consistently return false, provided no
information used in equals comparisons on the
objects is modified.
- For any non-null reference value
x,
x.equals(null) should return false.
An equivalence relation partitions the elements it operates on
into equivalence classes; all the members of an
equivalence class are equal to each other. Members of an
equivalence class are substitutable for each other, at least
for some purposes.
| Parameters |
|---|
o |
Object: the reference object with which to compare. |
| Returns |
|---|
boolean |
true if this object is the same as the obj
argument; false otherwise. |
hashCode
public int hashCode ()
Returns a hash code value for the object. This method is
supported for the benefit of hash tables such as those provided by
HashMap.
The general contract of hashCode is:
- Whenever it is invoked on the same object more than once during
an execution of a Java application, the
hashCode method
must consistently return the same integer, provided no information
used in equals comparisons on the object is modified.
This integer need not remain consistent from one execution of an
application to another execution of the same application.
- If two objects are equal according to the
equals method, then calling the hashCode method on each of the two objects must produce the
same integer result.
- It is not required that if two objects are unequal
according to the
equals method, then
calling the hashCode method on each of the two objects
must produce distinct integer results. However, the programmer
should be aware that producing distinct integer results for
unequal objects may improve the performance of hash tables.
| Returns |
|---|
int |
a hash code value for this object. |
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Last updated 2024-04-04 UTC.
