de.larssh.utils

Class Nullables

java.lang.Object

de.larssh.utils.Nullables

public final class Nullables
extends Object

This class contains helper methods for nullable values. It extends the functionality offered by Objects.

Method Summary

Modifier and Type	Method and Description
static <T> T	getFirst(Supplier<? extends T>... suppliers) Returns the first non-null value.
static <T> T	getFirst(T... values) Returns the first non-null value.
static <T> void	ifNonNull(T value, Consumer<? super T> consumer) If value is non-null, invoke the specified consumer with value, otherwise do nothing.
static <T> void	ifNonNullOrElse(T value, Consumer<? super T> action, Runnable emptyAction) If value is non-null, performs the given action with value, otherwise performs the given empty-based action.
static <T,U> U	map(T value, Function<? super T,? extends U> mapper) If value is non-null, apply the provided mapping function to it, and return the nullable result.
static <T> T	or(T value, Supplier<? extends T> supplier) If value is non-null, returns value, otherwise returns a nullable value produced by the supplying function.
static <T> T	orElse(T value, T other) Return value if non-null, otherwise return other.
static <T> T	orElseGet(T value, Supplier<? extends T> other) Return value if non-null, otherwise invoke other and return the result of that invocation.
static <T> T	orElseThrow(T value) If value is non-null, returns value, otherwise throws java.lang.NullPointerException.
static <T,X extends Throwable> T	orElseThrow(T value, Supplier<? extends X> exceptionSupplier) Return value, if non-null, otherwise throw an exception to be created by the provided supplier.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getFirst

@Nullable
 @SafeVarargs
public static <T> T getFirst(T... values)

Returns the first non-null value. Returns null if no value is non-null.

Type Parameters:

T - value type

Parameters:

values - any number of nullable values to test

Returns:

the first non-null value, null if no value is non-null

getFirst

@Nullable
 @SafeVarargs
public static <T> T getFirst(Supplier<? extends T>... suppliers)

Returns the first non-null value. Values are created on-demand by calling suppliers one after the other. Returns null if no value is non-null.

Type Parameters:

T - value type

Parameters:

suppliers - any number of value suppliers, which values to test, evaluated in a lazy manner

Returns:

the first non-null value, null if no value is non-null

ifNonNull

public static <T> void ifNonNull(@Nullable
                                 T value,
                                 Consumer<? super T> consumer)

If value is non-null, invoke the specified consumer with value, otherwise do nothing.

Type Parameters:

T - value type

Parameters:

value - nullable value

consumer - executed if value is null

ifNonNullOrElse

public static <T> void ifNonNullOrElse(@Nullable
                                       T value,
                                       Consumer<? super T> action,
                                       Runnable emptyAction)

If value is non-null, performs the given action with value, otherwise performs the given empty-based action.

Type Parameters:

T - value type

Parameters:

value - nullable value

action - the action to be performed, if value is non-null

emptyAction - the empty-based action to be performed, if value is null

map

@Nullable
public static <T,U> U map(@Nullable
                                    T value,
                                    Function<? super T,? extends U> mapper)

If value is non-null, apply the provided mapping function to it, and return the nullable result. Otherwise return null.

Type Parameters:

T - value type

U - the mapping functions result type

Parameters:

value - nullable value

mapper - a mapping function to apply to value, if non-null

Returns:

a nullable describing the result of applying a mapping function to value, if value is non-null, otherwise null

or

@Nullable
public static <T> T or(@Nullable
                                 T value,
                                 Supplier<? extends T> supplier)

If value is non-null, returns value, otherwise returns a nullable value produced by the supplying function.

Type Parameters:

T - value type

Parameters:

value - nullable value

supplier - the supplying function that produces a nullable value to be returned

Returns:

returns value, if value is non-null, otherwise a nullable value produced by the supplying function.

orElse

public static <T> T orElse(@Nullable
                           T value,
                           T other)

Return value if non-null, otherwise return other.

Type Parameters:

T - value type

Parameters:

value - nullable value

other - the value to be returned if value is null

Returns:

value, if non-null, otherwise other

orElseGet

public static <T> T orElseGet(@Nullable
                              T value,
                              Supplier<? extends T> other)

Return value if non-null, otherwise invoke other and return the result of that invocation.

Type Parameters:

T - value type

Parameters:

value - nullable value

other - a Supplier whose result is returned if value is null

Returns:

value if non-null otherwise the result of other.get()

orElseThrow

public static <T> T orElseThrow(@Nullable
                                T value)

If value is non-null, returns value, otherwise throws java.lang.NullPointerException.

Type Parameters:

T - value type

Parameters:

value - nullable value

Returns:

the non-null value held by value

Throws:

NullPointerException - if value is null

orElseThrow

public static <T,X extends Throwable> T orElseThrow(@Nullable
                                                    T value,
                                                    Supplier<? extends X> exceptionSupplier)
                                             throws X extends Throwable

Return value, if non-null, otherwise throw an exception to be created by the provided supplier.

Type Parameters:

T - value type

X - Type of the exception to be thrown

Parameters:

value - nullable value

exceptionSupplier - The supplier which will return the exception to be thrown

Returns:

the non-null value

Throws:

X - if value is null

X extends Throwable