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package com.sinch.sdk.core.models;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Supplier;
/**
* class adapted from {@link java.util.Optional} enabling to:
*
*
* - accept null value as authorized and defined value
*
- determine is a value was set with any value (null included) or not
*
*
* So, this class enable to distinguish a value set to null VS an undefined value
*
* @param the type of value
* @since 1.8
*/
public final class OptionalValue {
/** Common instance for {@code empty()}. */
private static final OptionalValue EMPTY = new OptionalValue<>();
/** If non-null, the value; if null, indicates no value is present */
private final T value;
private final boolean isSet;
/**
* Constructs an empty instance.
*
* @implNote Generally only one empty instance, {@link OptionalValue#EMPTY}, should exist per VM.
*/
private OptionalValue() {
this.value = null;
this.isSet = false;
}
/**
* Returns an empty {@code OptionalValue} instance. No value is present for this {@code Optional}.
*
* Though it may be tempting to do so, avoid testing if an object is empty by comparing with
* {@code ==} against instances returned by {@code Optional.empty()}. There is no guarantee that
* it is a singleton. Instead, use {@link #isPresent()}.
*
* @param The type of the non-existent value
* @return an empty {@code OptionalValue}
*/
public static OptionalValue empty() {
@SuppressWarnings("unchecked")
OptionalValue t = (OptionalValue) EMPTY;
return t;
}
/**
* Constructs an instance with the described value.
*
* @param value the value to describe
*/
private OptionalValue(T value) {
this.value = value;
this.isSet = true;
}
/**
* Returns an {@code OptionalValue} describing the given value.
*
* @param value the value to describe
* @param the type of the value
* @return an {@code OptionalValue} with the value present
*/
public static OptionalValue of(T value) {
return new OptionalValue<>(value);
}
/**
* If a value is present, returns the value, otherwise throws {@code NoSuchElementException}.
*
* The preferred alternative to this method is {@link #orElseThrow()}.
*
* @return the value described by this {@code OptionalValue}
* @throws NoSuchElementException if no value is present
*/
public T get() {
if (!this.isSet) {
throw new NoSuchElementException("No value present");
}
return value;
}
/**
* If a value is present, returns {@code true}, otherwise {@code false}.
*
* @return {@code true} if a value is present, otherwise {@code false}
*/
public boolean isPresent() {
return this.isSet;
}
/**
* If a value is present, performs the given action with the value, otherwise does nothing.
*
* @param action the action to be performed, if a value is present
* @throws NullPointerException if value is present and the given action is {@code null}
*/
public void ifPresent(Consumer action) {
if (this.isSet) {
action.accept(value);
}
}
/**
* If a value is set, performs the given action with the value, otherwise performs the given
* empty-based action.
*
* @param action the action to be performed, if a value is set
* @param emptyAction the empty-based action to be performed, if no value is present
* @throws NullPointerException if a value is present and the given action is {@code null}, or no
* value is present and the given empty-based action is {@code null}.
* @since 9
*/
public void ifPresentOrElse(Consumer action, Runnable emptyAction) {
if (this.isSet) {
action.accept(value);
} else {
emptyAction.run();
}
}
/**
* If a value is set, returns the value, otherwise returns {@code other}.
*
* @param other the value to be returned, if no value is present. May be {@code null}.
* @return the value, if present, otherwise {@code other}
*/
public T orElse(T other) {
return this.isSet ? value : other;
}
/**
* If a value is set, returns the value, otherwise returns the result produced by the supplying
* function.
*
* @param supplier the supplying function that produces a value to be returned
* @return the value, if present, otherwise the result produced by the supplying function
* @throws NullPointerException if no value is present and the supplying function is {@code null}
*/
public T orElseGet(Supplier supplier) {
return this.isSet ? value : supplier.get();
}
/**
* If a value is set, returns the value, otherwise throws {@code NoSuchElementException}.
*
* @return the non-{@code null} value described by this {@code Optional}
* @throws NoSuchElementException if no value is present
* @since 10
*/
public T orElseThrow() {
if (!this.isSet) {
throw new NoSuchElementException("No value present");
}
return value;
}
/**
* If a value is present, returns the value, otherwise throws an exception produced by the
* exception supplying function.
*
*
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 supplying function that produces an exception to be thrown
* @return the value, if present
* @throws X if no value is present
* @throws NullPointerException if no value is present and the exception supplying function is
* {@code null}
*/
public T orElseThrow(Supplier exceptionSupplier) throws X {
if (this.isSet) {
return value;
} else {
throw exceptionSupplier.get();
}
}
/**
* If a value is present, returns an {@code OptionalValue} describing the result of applying the
* given mapping function to the value, otherwise returns an empty {@code OptionalValue}.
*
* @param mapper the mapping function to apply to a value, if present
* @param The type of the value returned from the mapping function
* @return an {@code OptionalValue} describing the result of applying a mapping function to the
* value of this {@code OptionalValue}, if a value is present, otherwise an empty {@code
* OptionalValue}
* @throws NullPointerException if the mapping function is {@code null}
*/
public OptionalValue map(Function mapper) {
Objects.requireNonNull(mapper);
if (!isPresent()) {
return empty();
} else {
return OptionalValue.of(mapper.apply(value));
}
}
/**
* Indicates whether some other object is "equal to" this {@code Optional}. The other object is
* considered equal if:
*
*
* - it is also an {@code OptionalValue} and;
*
- both instances have no value set or;
*
- the present values are "equal to" each other via {@code equals()}.
*
*
* @param obj an object to be tested for equality
* @return {@code true} if the other object is "equal to" this object otherwise {@code false}
*/
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (!(obj instanceof OptionalValue)) {
return false;
}
OptionalValue other = (OptionalValue) obj;
return this.isSet == other.isSet && Objects.equals(value, other.value);
}
/**
* Returns the hash code of the value, if present, otherwise {@code 0} (zero) if no value is
* present.
*
* @return hash code value of the present value or {@code 0} if no value is present
*/
@Override
public int hashCode() {
return Objects.hashCode(isSet) + Objects.hashCode(value);
}
/**
* Returns a non-empty string representation of this {@code OptionalValue} suitable for debugging.
* The exact presentation format is unspecified and may vary between implementations and versions.
*
* If a value is set the result must include its string representation in the result. undefined
* and defined (set) {@code OptionalValue}s must be unambiguously differentiable.
*
* @return the string representation of this instance
*/
@Override
public String toString() {
return this.isSet ? String.format("OptionalValue[%s]", value) : "OptionalValue.undefined";
}
}