- java.lang.Object
-
- java.util.Objects
-
public final class Objects extends Object
This class consists ofstatic
utility methods for operating on objects. These utilities includenull
-safe ornull
-tolerant methods for computing the hash code of an object, returning a string for an object, and comparing two objects.- Since:
- 1.7
-
-
Method Summary
Methods Modifier and Type Method and Description static <T> int
compare(T a, T b, Comparator<? super T> c)
Returns 0 if the arguments are identical andc.compare(a, b)
otherwise.static boolean
deepEquals(Object a, Object b)
Returnstrue
if the arguments are deeply equal to each other andfalse
otherwise.static boolean
equals(Object a, Object b)
Returnstrue
if the arguments are equal to each other andfalse
otherwise.static int
hash(Object... values)
Generates a hash code for a sequence of input values.static int
hashCode(Object o)
Returns the hash code of a non-null
argument and 0 for anull
argument.static <T> T
requireNonNull(T obj)
Checks that the specified object reference is notnull
.static <T> T
requireNonNull(T obj, String message)
Checks that the specified object reference is notnull
and throws a customizedNullPointerException
if it is.static String
toString(Object o)
Returns the result of callingtoString
for a non-null
argument and"null"
for anull
argument.static String
toString(Object o, String nullDefault)
Returns the result of callingtoString
on the first argument if the first argument is notnull
and returns the second argument otherwise.
-
-
-
Method Detail
-
equals
public static boolean equals(Object a, Object b)
Returnstrue
if the arguments are equal to each other andfalse
otherwise. Consequently, if both arguments arenull
,true
is returned and if exactly one argument isnull
,false
is returned. Otherwise, equality is determined by using theequals
method of the first argument.- Parameters:
a
- an objectb
- an object to be compared witha
for equality- Returns:
true
if the arguments are equal to each other andfalse
otherwise- See Also:
Object.equals(Object)
-
deepEquals
public static boolean deepEquals(Object a, Object b)
Returnstrue
if the arguments are deeply equal to each other andfalse
otherwise. Twonull
values are deeply equal. If both arguments are arrays, the algorithm inArrays.deepEquals
is used to determine equality. Otherwise, equality is determined by using theequals
method of the first argument.- Parameters:
a
- an objectb
- an object to be compared witha
for deep equality- Returns:
true
if the arguments are deeply equal to each other andfalse
otherwise- See Also:
Arrays.deepEquals(Object[], Object[])
,equals(Object, Object)
-
hashCode
public static int hashCode(Object o)
Returns the hash code of a non-null
argument and 0 for anull
argument.- Parameters:
o
- an object- Returns:
- the hash code of a non-
null
argument and 0 for anull
argument - See Also:
Object.hashCode()
-
hash
public static int hash(Object... values)
Generates a hash code for a sequence of input values. The hash code is generated as if all the input values were placed into an array, and that array were hashed by callingArrays.hashCode(Object[])
.This method is useful for implementing
Object.hashCode()
on objects containing multiple fields. For example, if an object that has three fields,x
,y
, andz
, one could write:
Warning: When a single object reference is supplied, the returned value does not equal the hash code of that object reference. This value can be computed by calling@Override public int hashCode() { return Objects.hash(x, y, z); }
hashCode(Object)
.- Parameters:
values
- the values to be hashed- Returns:
- a hash value of the sequence of input values
- See Also:
Arrays.hashCode(Object[])
,List.hashCode()
-
toString
public static String toString(Object o)
Returns the result of callingtoString
for a non-null
argument and"null"
for anull
argument.- Parameters:
o
- an object- Returns:
- the result of calling
toString
for a non-null
argument and"null"
for anull
argument - See Also:
Object.toString()
,String.valueOf(Object)
-
toString
public static String toString(Object o, String nullDefault)
Returns the result of callingtoString
on the first argument if the first argument is notnull
and returns the second argument otherwise.- Parameters:
o
- an objectnullDefault
- string to return if the first argument isnull
- Returns:
- the result of calling
toString
on the first argument if it is notnull
and the second argument otherwise. - See Also:
toString(Object)
-
compare
public static <T> int compare(T a, T b, Comparator<? super T> c)
Returns 0 if the arguments are identical andc.compare(a, b)
otherwise. Consequently, if both arguments arenull
0 is returned.Note that if one of the arguments is
null
, aNullPointerException
may or may not be thrown depending on what ordering policy, if any, theComparator
chooses to have fornull
values.- Type Parameters:
T
- the type of the objects being compared- Parameters:
a
- an objectb
- an object to be compared witha
c
- theComparator
to compare the first two arguments- Returns:
- 0 if the arguments are identical and
c.compare(a, b)
otherwise. - See Also:
Comparable
,Comparator
-
requireNonNull
public static <T> T requireNonNull(T obj)
Checks that the specified object reference is notnull
. This method is designed primarily for doing parameter validation in methods and constructors, as demonstrated below:public Foo(Bar bar) { this.bar = Objects.requireNonNull(bar); }
- Type Parameters:
T
- the type of the reference- Parameters:
obj
- the object reference to check for nullity- Returns:
obj
if notnull
- Throws:
NullPointerException
- ifobj
isnull
-
requireNonNull
public static <T> T requireNonNull(T obj, String message)
Checks that the specified object reference is notnull
and throws a customizedNullPointerException
if it is. This method is designed primarily for doing parameter validation in methods and constructors with multiple parameters, as demonstrated below:public Foo(Bar bar, Baz baz) { this.bar = Objects.requireNonNull(bar, "bar must not be null"); this.baz = Objects.requireNonNull(baz, "baz must not be null"); }
- Type Parameters:
T
- the type of the reference- Parameters:
obj
- the object reference to check for nullitymessage
- detail message to be used in the event that aNullPointerException
is thrown- Returns:
obj
if notnull
- Throws:
NullPointerException
- ifobj
isnull
-
-
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Document heeft de 11/06/2005 gemaakt, de laatste keer de 04/03/2020 gewijzigd
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