Package org.checkerframework.checker.nullness.util

Class Opt

java.lang.Object

org.checkerframework.checker.nullness.util.Opt

@AnnotatedFor("nullness")
public final class Opt
extends Object

Utility class providing every method in Optional, but written for possibly-null references rather than for the Optional type.

To avoid the need to write the Opt class name at invocation sites, do:

import static org.checkerframework.checker.nullness.util.Opt.orElse;

or

import static org.checkerframework.checker.nullness.util.Opt.*;

Runtime Dependency: If you use this class, you must distribute (or link to) checker-qual.jar, along with your binaries. Or, you can copy this class into your own project.

See Also:

• Optional

Method Summary

Modifier and Type	Method	Description
static <T> @Nullable T	filter(T primary, Predicate<@NonNull ? super @NonNull T> predicate)	If primary is non-null, and its value matches the given predicate, return the value.
static <T extends @NonNull Object> T	get(T primary)	If primary is non-null, returns it, otherwise throws NoSuchElementException.
static <T> void	ifPresent(T primary, Consumer<@NonNull ? super @NonNull T> consumer)	If primary is non-null, invoke the specified consumer with the value, otherwise do nothing.
static <T> void	ifPresentOrElse(T primary, Consumer<@NonNull ? super @NonNull T> action, Runnable emptyAction)	If primary is non-null, invoke the specified consumer with the value, otherwise invoke the empty action.
static boolean	isPresent(@Nullable Object primary)	Returns true if primary is non-null, false if primary is null.
static <T, U> @Nullable U	map(T primary, Function<@NonNull ? super @NonNull T,? extends U> mapper)	If primary is non-null, apply the provided mapping function to it and return the result.
static <T> @NonNull T	orElse(T primary, @NonNull T other)	Returns primary if it is non-null.
static <T> @NonNull T	orElseGet(T primary, Supplier<? extends @NonNull T> other)	Returns primary if it is non-null.
static <T extends @NonNull Object, X extends @NonNull Throwable> T	orElseThrow(T primary, Supplier<? extends X> exceptionSupplier)	Returns primary if it is non-null.

Methods inherited from class java.lang.Object

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

Method Details

get

public static <T extends @NonNull Object> T get(T primary)

If primary is non-null, returns it, otherwise throws NoSuchElementException.

Type Parameters:

T - the type of the argument

Parameters:

primary - a non-null value to return

Returns:

primary if it is non-null

Throws:

NoSuchElementException - if primary is null

See Also:

• Optional.get()

isPresent

@EnsuresNonNullIf(expression="#1",
                  result=true)
public static boolean isPresent(@Nullable Object primary)

Returns true if primary is non-null, false if primary is null.

See Also:

• Optional.isPresent()

ifPresent

public static <T> void ifPresent(T primary,
 Consumer<@NonNull ? super @NonNull T> consumer)

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

See Also:

• Optional.ifPresent(Consumer)

ifPresentOrElse

public static <T> void ifPresentOrElse(T primary,
 Consumer<@NonNull ? super @NonNull T> action,
 Runnable emptyAction)

If primary is non-null, invoke the specified consumer with the value, otherwise invoke the empty action.

Type Parameters:

T - the type of the argument

Parameters:

primary - the nullable value

action - the consumer to be executed if primary is non-null

emptyAction - the action to be executed if primary is null

See Also:

• Optional.ifPresentOrElse(Consumer, Runnable)

filter

public static <T> @Nullable T filter(T primary,
 Predicate<@NonNull ? super @NonNull T> predicate)

If primary is non-null, and its value matches the given predicate, return the value. If primary is null or its non-null value does not match the predicate, return null.

See Also:

• Optional.filter(Predicate)

map

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

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

See Also:

• Optional.map(Function)

orElse

public static <T> @NonNull T orElse(T primary,
 @NonNull T other)

Returns primary if it is non-null. If primary is null, return other.

See Also:

• Optional.orElse(Object)

orElseGet

public static <T> @NonNull T orElseGet(T primary,
 Supplier<? extends @NonNull T> other)

Returns primary if it is non-null. If primary is null, invoke other and return the result of that invocation.

See Also:

• Optional.orElseGet(Supplier)

orElseThrow

public static <T extends @NonNull Object,
X extends @NonNull Throwable>
T orElseThrow(T primary,
 Supplier<? extends X> exceptionSupplier)
       throws X

Returns primary if it is non-null. If primary is null, throw an exception to be created by the provided supplier.

Throws:

X

See Also:

• Optional.orElseThrow(Supplier)