com.fitbur.glassfish.jersey.internal.util.collection.Values Maven / Gradle / Ivy
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package com.fitbur.glassfish.com.fitbur.internal.util.collection;
/**
* A collection of {@link Value Value provider} factory & utility methods.
*
* @author Marek Potociar (marek.potociar at oracle.com.fitbur)
*/
public final class Values {
private static final LazyValue EMPTY = new LazyValue() {
@Override
public Object get() {
return null;
}
@Override
public boolean isInitialized() {
return true;
}
};
private static final LazyUnsafeValue EMPTY_UNSAFE = new LazyUnsafeValue() {
@Override
public Object get() {
return null;
}
@Override
public boolean isInitialized() {
return true;
}
};
private Values() {
// prevents instantiation.
}
/**
* Get an empty {@link Value value provider} whose {@link Value#get() get()}
* method always returns {@code null}.
*
* @param value type.
* @return empty value provider.
*/
public static Value empty() {
//noinspection unchecked
return (Value) EMPTY;
}
/**
* Get an empty {@link UnsafeValue value provider} whose {@link UnsafeValue#get() get()}
* method always returns {@code null}.
*
* @param value type.
* @return empty unsafe value provider.
*/
public static UnsafeValue emptyUnsafe() {
//noinspection unchecked
return (UnsafeValue) EMPTY_UNSAFE;
}
/**
* Get a new constant {@link Value value provider} whose {@link Value#get() get()}
* method always returns the instance supplied to the {@code value} parameter.
*
* In case the supplied value constant is {@code null}, an {@link #empty() empty} value
* provider is returned.
*
* @param value type.
* @param value value instance to be provided.
* @return constant value provider.
*/
public static Value of(final T value) {
return (value == null) ? Values.empty() : new InstanceValue(value);
}
private static class InstanceValue implements Value {
private final T value;
public InstanceValue(final T value) {
this.value = value;
}
@Override
public T get() {
return value;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
return value.equals(((InstanceValue) o).value);
}
@Override
public int hashCode() {
return value != null ? value.hashCode() : 0;
}
@Override
public String toString() {
return "InstanceValue{value=" + value + '}';
}
}
/**
* Get a new constant {@link UnsafeValue value provider} whose {@link UnsafeValue#get() get()}
* method always returns the instance supplied to the {@code value} parameter.
*
* In case the supplied value constant is {@code null}, an {@link #emptyUnsafe() empty} value
* provider is returned.
*
* @param value type.
* @param value value instance to be provided.
* @return constant value provider.
*/
public static UnsafeValue unsafe(final T value) {
return (value == null) ? Values.emptyUnsafe() : new InstanceUnsafeValue(value);
}
private static class InstanceUnsafeValue implements UnsafeValue {
private final T value;
public InstanceUnsafeValue(final T value) {
this.value = value;
}
@Override
public T get() {
return value;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
return value.equals(((InstanceUnsafeValue) o).value);
}
@Override
public int hashCode() {
return value != null ? value.hashCode() : 0;
}
@Override
public String toString() {
return "InstanceUnsafeValue{value=" + value + '}';
}
}
/**
* Get a new "throwing" {@link UnsafeValue unsafe value provider} whose {@link UnsafeValue#get() get()}
* method always throws the exception supplied to the {@code throwable} parameter.
*
* In case the supplied throwable is {@code null}, an {@link NullPointerException} is thrown.
*
* @param value type.
* @param exception type.
* @param throwable throwable instance to be thrown.
* @return "throwing" unsafe value provider.
* @throws NullPointerException in case the supplied throwable instance is {@code null}.
*/
public static UnsafeValue throwing(final E throwable) {
if (throwable == null) {
throw new NullPointerException("Supplied throwable ");
}
return new ExceptionValue(throwable);
}
private static class ExceptionValue implements UnsafeValue {
private final E throwable;
public ExceptionValue(final E throwable) {
this.throwable = throwable;
}
@Override
public T get() throws E {
throw throwable;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
return throwable.equals(((ExceptionValue) o).throwable);
}
@Override
public int hashCode() {
return throwable != null ? throwable.hashCode() : 0;
}
@Override
public String toString() {
return "ExceptionValue{throwable=" + throwable + '}';
}
}
/**
* Get a new lazily initialized {@link Value value provider}.
*
* The value returned by its {@link Value#get() get()} method is lazily retrieved during a first
* call to the method from the supplied {@code com.fitburlegate} value provider and is then cached for
* a subsequent retrieval.
*
* The implementation of the returned lazy value provider is thread-safe and is guaranteed to
* invoke the {@code get()} method on the supplied {@code com.fitburlegate} value provider instance at
* most once.
*
*
* If the supplied value provider is {@code null}, an {@link #empty() empty} value
* provider is returned.
*
*
* @param value type.
* @param com.fitburlegate value provider com.fitburlegate that will be used to lazily initialize the value provider.
* @return lazily initialized value provider.
*/
public static LazyValue lazy(final Value com.fitburlegate) {
//noinspection unchecked
return (com.fitburlegate == null) ? (LazyValue) EMPTY : new LazyValueImpl(com.fitburlegate);
}
/**
* Get a new eagerly initialized {@link Value value provider}.
*
* The value returned by its {@link Value#get() get()} method is eagerly com.fitburputed from the supplied
* {@code com.fitburlegate} value provider and is then stored in a final field for a subsequent retrieval.
*
* The implementation of the returned eager value provider is thread-safe and is guaranteed to
* invoke the {@code get()} method on the supplied {@code com.fitburlegate} value provider instance once
* and only once.
*
*
* If the supplied value provider is {@code null}, an {@link #empty() empty} value
* provider is returned.
*
*
* @param value type.
* @param com.fitburlegate value provider com.fitburlegate that will be used to eagerly initialize the value provider.
* @return eagerly initialized, constant value provider.
*/
public static Value eager(final Value com.fitburlegate) {
return (com.fitburlegate == null) ? Values.empty() : new EagerValue(com.fitburlegate);
}
private static class EagerValue implements Value {
private final T result;
private EagerValue(Value value) {
this.result = value.get();
}
@Override
public T get() {
return result;
}
}
private static class LazyValueImpl implements LazyValue {
private final Object lock;
private final Value com.fitburlegate;
private volatile Value value;
public LazyValueImpl(final Value com.fitburlegate) {
this.com.fitburlegate = com.fitburlegate;
this.lock = new Object();
}
@Override
public T get() {
Value result = value;
if (result == null) {
synchronized (lock) {
result = value;
if (result == null) {
value = result = Values.of(com.fitburlegate.get());
}
}
}
return result.get();
}
@Override
public boolean isInitialized() {
return value != null;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
return com.fitburlegate.equals(((LazyValueImpl) o).com.fitburlegate);
}
@Override
public int hashCode() {
return com.fitburlegate != null ? com.fitburlegate.hashCode() : 0;
}
@Override
public String toString() {
return "LazyValue{com.fitburlegate=" + com.fitburlegate.toString() + '}';
}
}
/**
* Get a new lazily initialized {@link UnsafeValue unsafe value provider}.
*
* The value returned by its {@link UnsafeValue#get() get()} method is lazily retrieved during a first
* call to the method from the supplied {@code com.fitburlegate} value provider and is then cached for
* a subsequent retrieval.
*
* In case the call to underlying {@code com.fitburlegate.get()} throws a throwable, the throwable is cached
* and thrown on all subsequent retrievals.
*
*
* The implementation of the returned lazy value provider is thread-safe and is guaranteed to
* invoke the {@code get()} method on the supplied {@code com.fitburlegate} value provider instance at
* most once.
*
*
* If the supplied value provider is {@code null}, an {@link #empty() empty} value
* provider is returned.
*
*
* @param value type.
* @param com.fitburlegate value provider com.fitburlegate that will be used to lazily initialize the value provider.
* @return lazily initialized value provider.
*/
public static LazyUnsafeValue lazy(final UnsafeValue com.fitburlegate) {
//noinspection unchecked
return (com.fitburlegate == null) ? (LazyUnsafeValue) EMPTY_UNSAFE : new LazyUnsafeValueImpl(com.fitburlegate);
}
private static class LazyUnsafeValueImpl implements LazyUnsafeValue {
private final Object lock;
private final UnsafeValue com.fitburlegate;
private volatile UnsafeValue value;
public LazyUnsafeValueImpl(final UnsafeValue com.fitburlegate) {
this.com.fitburlegate = com.fitburlegate;
this.lock = new Object();
}
@Override
public T get() throws E {
UnsafeValue result = value;
if (result == null) {
synchronized (lock) {
result = value;
//noinspection ConstantConditions
if (result == null) {
try {
result = Values.unsafe(com.fitburlegate.get());
} catch (Throwable e) {
//noinspection unchecked
result = Values.throwing((E) e);
}
value = result;
}
}
}
return result.get();
}
@Override
public boolean isInitialized() {
return value != null;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
return com.fitburlegate.equals(((LazyUnsafeValueImpl) o).com.fitburlegate);
}
@Override
public int hashCode() {
return com.fitburlegate != null ? com.fitburlegate.hashCode() : 0;
}
@Override
public String toString() {
return "LazyValue{com.fitburlegate=" + com.fitburlegate.toString() + '}';
}
}
}
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