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A general programming library in Java
package com.landawn.abacus.util;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Set;
import com.landawn.abacus.annotation.Beta;
import com.landawn.abacus.util.function.Supplier;
import com.landawn.abacus.util.stream.Stream;
@Beta
abstract class Any {
final T value;
final boolean isPresent;
/**
* Constructs an empty instance.
*
* @implNote Generally only one empty instance, {@link Any#EMPTY},
* should exist per VM.
*/
Any() {
this.value = null;
isPresent = false;
}
/**
* Constructs an instance with the value present.
*
* @param value the nullable value to be present
*/
Any(T value) {
this.value = value;
isPresent = true;
}
/**
* Returns an empty {@code Any} instance. No value is present for this
* Optional.
*
* @apiNote Though it may be tempting to do so, avoid testing if an object
* is empty by comparing with {@code ==} against instances returned by
* {@code Any.empty()}. There is no guarantee that it is a singleton.
* Instead, use {@link #isPresent()}.
*
* @param Type of the non-existent value
* @return an empty {@code Any}
*/
public static Any empty() {
return Nullable.empty();
}
/**
* Returns an {@code Any} with the specified present nullable value.
*
* @param value the value to be present, which could be null
* @return an {@code Any} with the value present
*/
public static Any of(T value) {
return Nullable.of(value);
}
/**
* If a value is present in this {@code Any}, returns the value,
* otherwise throws {@code NoSuchElementException}.
*
* @return the nullable value held by this {@code Any}
* @throws NoSuchElementException if there is no value present
*
* @see Any#isPresent()
*/
public T get() {
if (isPresent()) {
return value;
} else {
throw new NoSuchElementException("No value present");
}
}
/**
* Return {@code true} if there is a value present, otherwise {@code false}.
*
* @return {@code true} if there is a value present, otherwise {@code false}
*/
public boolean isPresent() {
return isPresent;
}
/**
* Return {@code true} if there is a value not null, otherwise {@code false}.
*
* @return {@code true} if there is a value not null, otherwise {@code false}
*/
public boolean isNotNull() {
return value != null;
}
/**
* If a value is present, invoke the specified consumer with the value,
* otherwise do nothing.
*
* @param consumer block to be executed if a value is present
* @throws NullPointerException if value is present and {@code consumer} is
* null
*/
public void ifPresent(Try.Consumer consumer) throws E {
if (isPresent()) {
consumer.accept(value);
}
}
/**
* If a value is present, performs the given action with the value, otherwise performs the given empty-based action.
*
* @param action
* @param emptyAction
*/
public void ifPresentOrElse(Try.Consumer action, Try.Runnable emptyAction) throws E, E2 {
if (isPresent()) {
action.accept(value);
} else {
emptyAction.run();
}
}
/**
* If a value is not null, invoke the specified consumer with the value,
* otherwise do nothing.
*
* @param consumer block to be executed if a value is not null.
* @throws NullPointerException if value is present and {@code consumer} is
* null
*/
public void ifNotNull(Try.Consumer consumer) throws E {
if (isNotNull()) {
consumer.accept(value);
}
}
/**
* If a value is not null, performs the given action with the value, otherwise performs the given empty-based action.
*
* @param action
* @param emptyAction
*/
public void ifNotNullOrElse(Try.Consumer action, Try.Runnable emptyAction) throws E, E2 {
if (isNotNull()) {
action.accept(value);
} else {
emptyAction.run();
}
}
/**
* If a value is present, and the value matches the given predicate,
* return an {@code Any} describing the value, otherwise return an
* empty {@code Any}.
*
* @param predicate a predicate to apply to the value, if present
* @return an {@code Any} describing the value of this {@code Any}
* if a value is present and the value matches the given predicate,
* otherwise an empty {@code Any}
* @throws NullPointerException if the predicate is null
*/
public abstract Any filter(Try.Predicate predicate) throws E;
/**
* If a value is present, apply the provided mapping function to it,
*
* @apiNote This method supports post-processing on optional values, without
* the need to explicitly check for a return status. For example, the
* following code traverses a stream of file names, selects one that has
* not yet been processed, and then opens that file, returning an
* {@code Optional}:
*
* {@code
* Any fis =
* names.stream().filter(name -> !isProcessedYet(name))
* .findFirst()
* .map(name -> new FileInputStream(name));
* }
*
* Here, {@code findFirst} returns an {@code Any}, and then
* {@code map} returns an {@code Any} for the desired
* file if one exists.
*
* @param The type of the result of the mapping function
* @param mapper a mapping function to apply to the value, if present
* @return an {@code Any} describing the result of applying a mapping
* function to the value of this {@code Any}, if a value is present,
* otherwise an empty {@code Any}
* @throws NullPointerException if the mapping function is null
*/
public abstract Any map(Try.Function mapper) throws E;
/**
* If a value is present, apply the provided {@code Any}-bearing
* mapping function to it, return that result, otherwise return an empty
* {@code Any}. This method is similar to {@link #map(Function)},
* but the provided mapper is one whose result is already an {@code Any},
* and if invoked, {@code flatMap} does not wrap it with an additional
* {@code Any}.
*
* @param The type parameter to the {@code Any} returned by
* @param mapper a mapping function to apply to the value, if present
* the mapping function
* @return the result of applying an {@code Any}-bearing mapping
* function to the value of this {@code Any}, if a value is present,
* otherwise an empty {@code Any}
* @throws NullPointerException if the mapping function is null or returns
* a null result
*/
public abstract Any flatMap(Try.Function, E> mapper) throws E;
/**
* If a value is not null, and the value matches the given predicate,
* return an {@code Any} describing the value, otherwise return an
* empty {@code Any}.
*
* @param predicate a predicate to apply to the value, if present
* @return an {@code Any} describing the value of this {@code Any}
* if a value is present and the value matches the given predicate,
* otherwise an empty {@code Any}
* @throws NullPointerException if the predicate is null
*/
public abstract Any filterIfNotNull(Try.Predicate predicate) throws E;
/**
* If a value is not null, apply the provided mapping function to it,
*
* @apiNote This method supports post-processing on optional values, without
* the need to explicitly check for a return status. For example, the
* following code traverses a stream of file names, selects one that has
* not yet been processed, and then opens that file, returning an
* {@code Optional}:
*
* {@code
* Any fis =
* names.stream().filter(name -> !isProcessedYet(name))
* .findFirst()
* .map(name -> new FileInputStream(name));
* }
*
* Here, {@code findFirst} returns an {@code Any}, and then
* {@code map} returns an {@code Optional} for the desired
* file if one exists.
*
* @param The type of the result of the mapping function
* @param mapper a mapping function to apply to the value, if not null
* @return an {@code Any} describing the result of applying a mapping
* function to the value of this {@code Any}, if a value is not null,
* otherwise an empty {@code Any}
* @throws NullPointerException if the mapping function is null
*/
public abstract Any mapIfNotNull(Try.Function mapper) throws E;
/**
* If a value is not null, apply the provided {@code Any}-bearing
* mapping function to it, return that result, otherwise return an empty
* {@code Any}. This method is similar to {@link #map(Function)},
* but the provided mapper is one whose result is already an {@code Any},
* and if invoked, {@code flatMap} does not wrap it with an additional
* {@code Any}.
*
* @param The type parameter to the {@code Any} returned by
* @param mapper a mapping function to apply to the value, if not null
* the mapping function
* @return the result of applying an {@code Any}-bearing mapping
* function to the value of this {@code Any}, if a value is not null,
* otherwise an empty {@code Any}
* @throws NullPointerException if the mapping function is null or returns
* a null result
*/
public abstract Any flatMapIfNotNull(Try.Function, E> mapper) throws E;
/**
* If a value is present, returns an Optional describing the value, otherwise returns an Optional produced by the supplying function.
*
* @param supplier
* @return
* @throws E
*/
public abstract Any or(Try.Supplier, E> supplier) throws E;
public T orNull() {
return isPresent() ? value : null;
}
/**
* Return the value if present, otherwise return {@code other}.
*
* @param other the value to be returned if there is no value present, may be null
* @return the value, if present, otherwise {@code other}
*/
public T orElse(T other) {
return isPresent() ? value : other;
}
/**
* Return the value if present, otherwise invoke {@code other} and return the result of that invocation.
*
* @param other a {@code Supplier} whose result is returned if no value is present
* @return the value if present otherwise the result of {@code other.get()}
* @throws NullPointerException if value is not present and {@code other} is
* null
*/
public T orElseGet(Try.Supplier other) throws E {
return isPresent() ? value : other.get();
}
/**
* Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.
*
* @apiNote A method reference to the exception constructor with an empty
* argument list can be used as the supplier. For example,
* {@code IllegalStateException::new}
*
* @param Type of the exception to be thrown
* @param exceptionSupplier The supplier which will return the exception to
* be thrown
* @return the present value
* @throws X if there is no value present
* @throws NullPointerException if no value is present and
* {@code exceptionSupplier} is null
*/
public T orElseThrow(Supplier exceptionSupplier) throws X {
if (isPresent()) {
return value;
} else {
throw exceptionSupplier.get();
}
}
/**
* Return the value is not null, otherwise return {@code other}.
*
* @param other the value to be returned if not present or null, may be null
* @return the value, if not present or null, otherwise {@code other}
*/
public T orIfNull(T other) {
return isNotNull() ? value : other;
}
/**
* Return the value is not null, otherwise invoke {@code other} and return the result of that invocation.
*
* @param other a {@code Supplier} whose result is returned if not present or null
* @return the value if not present or null otherwise the result of {@code other.get()}
* @throws NullPointerException if value is not present and {@code other} is null
*/
public T orGetIfNull(Try.Supplier other) throws E {
return isNotNull() ? value : other.get();
}
/**
* Return the value is not null, otherwise throw an exception to be created by the provided supplier.
*
* @apiNote A method reference to the exception constructor with an empty
* argument list can be used as the supplier. For example,
* {@code IllegalStateException::new}
*
* @param Type of the exception to be thrown
* @param exceptionSupplier The supplier which will return the exception to be thrown
* @return the present value
* @throws X if not present or null
* @throws NullPointerException if not present or null and
* {@code exceptionSupplier} is null
*/
public T orThrowIfNull(Supplier exceptionSupplier) throws X {
if (isNotNull()) {
return value;
} else {
throw exceptionSupplier.get();
}
}
/**
*
* @return an empty stream if it's not present.
*/
public Stream stream() {
return isPresent() ? Stream.of(value) : Stream. empty();
}
/**
*
* @return an empty stream if it's null.
*/
public Stream streamIfNotNull() {
return isNotNull() ? Stream.of(value) : Stream. empty();
}
/**
* Returns a {@code List} with the value if it presents, otherwise an empty {@code List}.
*
* @return
*/
public List toList() {
return isPresent() ? N.asList(value) : new ArrayList();
}
/**
* Returns a {@code List} with the value if the value is not null, otherwise an empty {@code List}.
*
* @return
*/
public List toListIfNotNull() {
return isNotNull() ? N.asList(value) : new ArrayList();
}
/**
* Returns a {@code Set} with the value if it presents, otherwise an empty {@code Set}.
*
* @return
*/
public Set toSet() {
return isPresent() ? N.asSet(value) : new HashSet();
}
/**
* Returns a {@code Set} with the value if the value is not null, otherwise an empty {@code Set}.
*
* @return
*/
public Set toSetIfNotNull() {
return isNotNull() ? N.asSet(value) : new HashSet();
}
/**
*
* @return Optional.empty() if the value is not present or {@code null}.
*/
public Optional toOptional() {
return value == null ? Optional. empty() : Optional.of(value);
}
/**
*
* @return java.util.Optional.empty() if the value is not present or {@code null}.
*/
public java.util.Optional toJdkOptional() {
return value == null ? java.util.Optional. empty() : java.util.Optional.of(value);
}
}
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