org.d2ab.util.primitive.OptionalChar Maven / Gradle / Ivy
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/*
* Copyright 2015 Daniel Skogquist Åborg
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.d2ab.util.primitive;
import org.d2ab.function.chars.CharConsumer;
import org.d2ab.function.chars.CharSupplier;
import java.util.NoSuchElementException;
import java.util.function.Supplier;
/**
* A container object which may or may not contain a {@code char} value. If a value is present, {@code isPresent()} will
* return {@code true} and {@code getAsChar()} will return the value.
*
*
Additional methods that depend on the presence or absence of a contained value are provided, such as {@link
* #orElse(char) orElse()} (return a default value if value not present) and {@link #ifPresent(CharConsumer)
* ifPresent()} (execute a block of code if the value is present).
*
*
This is a value-based class; use of identity-sensitive operations
* (including reference equality ({@code ==}), identity hash code, or synchronization) on instances of {@code
* OptionalChar} may have unpredictable results and should be avoided.
*
* @since 1.8
*/
public final class OptionalChar {
private static final int CACHE_THRESHOLD = 0x100;
private static final OptionalChar[] CACHE = buildCache(CACHE_THRESHOLD);
/**
* Common instance for {@code empty()}.
*/
private static final OptionalChar EMPTY = new OptionalChar();
/**
* If true then the value is present, otherwise indicates no value is present
*/
private final boolean present;
private final char value;
/**
* Construct an empty instance.
*
* @implNote Generally only one empty instance, {@link OptionalChar#EMPTY}, should exist per VM.
*/
private OptionalChar() {
this.present = false;
this.value = 0;
}
/**
* Construct an instance with the value present.
*
* @param value the char value to be present
*/
private OptionalChar(char value) {
this.present = true;
this.value = value;
}
private static OptionalChar[] buildCache(int threshold) {
OptionalChar[] cache = new OptionalChar[threshold];
for (int i = 0; i < threshold; i++) {
cache[i] = new OptionalChar((char) i);
}
return cache;
}
/**
* Returns an empty {@code OptionalChar} instance. No value is present for this OptionalChar.
*
* Though it may be tempting to do so, avoid testing if an object is empty by comparing with {@code ==}
* against instances returned by {@code Option.empty()}. There is no guarantee that it is a singleton. Instead, use
* {@link #isPresent()}.
*
* @return an empty {@code OptionalChar}
*/
public static OptionalChar empty() {
return EMPTY;
}
/**
* Return an {@code OptionalChar} with the specified value present.
*
* @param value the value to be present
*
* @return an {@code OptionalChar} with the value present
*/
public static OptionalChar of(char value) {
return value < CACHE_THRESHOLD ? CACHE[(int) value] : new OptionalChar(value);
}
/**
* If a value is present in this {@code OptionalChar}, returns the value, otherwise throws {@code
* NoSuchElementException}.
*
* @return the value held by this {@code OptionalChar}
*
* @throws NoSuchElementException if there is no value present
* @see OptionalChar#isPresent()
*/
public char getAsChar() {
if (!present)
throw new NoSuchElementException("No value present");
return value;
}
/**
* 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 present;
}
/**
* Have the specified consumer accept the value if a value is present, 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(CharConsumer consumer) {
if (present)
consumer.accept(value);
}
/**
* Return the value if present, otherwise return {@code other}.
*
* @param other the value to be returned if there is no value present
*
* @return the value, if present, otherwise {@code other}
*/
public char orElse(char other) {
return present ? value : other;
}
/**
* Return the value if present, otherwise invoke {@code other} and return the result of that invocation.
*
* @param other a {@code CharSupplier} whose result is returned if no value is present
*
* @return the value if present otherwise the result of {@code other.getAsChar()}
*
* @throws NullPointerException if value is not present and {@code other} is null
*/
public char orElseGet(CharSupplier other) {
return present ? value : other.getAsChar();
}
/**
* Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.
*
* 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 char orElseThrow(Supplier exceptionSupplier) throws X {
if (present)
return value;
else
throw exceptionSupplier.get();
}
/**
* Returns the hash code value of the present value, if any, or 0 (zero) if no value is present.
*
* @return hash code value of the present value or 0 if no value is present
*/
@Override
public int hashCode() {
return present ? Character.hashCode(value) : 0;
}
/**
* Indicates whether some other object is "equal to" this OptionalChar. The other object is considered equal if:
* - it is also an {@code OptionalChar} and;
- both instances have no value present or;
- the present
* values are "equal to" each other via {@code ==}.
*
* @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 OptionalChar))
return false;
OptionalChar other = (OptionalChar) obj;
return (present && other.present) ? value == other.value : present == other.present;
}
/**
* {@inheritDoc}
*
* Returns a non-empty string representation of this object suitable for debugging. The exact presentation
* format is
* unspecified and may vary between implementations and versions.
*
* If a value is present the result must include its string representation in the result. Empty and
* present instances must be unambiguously differentiable.
*
* @return the string representation of this instance
*/
@Override
public String toString() {
return present ? String.format("OptionalChar[%s]", value) : "OptionalChar.empty";
}
}