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package bjc.utils.data;
import java.util.function.Consumer;
import java.util.function.Function;
/**
* Holds a single value of a specific type. This is used for indirect
* references to data, and more specifically for accessing non-final
* variables from a lambda. AKA the identity monad
*
* This is an eager variant of {@link IHolder}
*
* @author ben
*
* @param <T>
* The type of the data being held
*/
public class GenHolder<T> implements IHolder<T> {
/**
* The state this holder is responsible for.
*/
private T heldValue;
/**
* Creates a new empty holder, with its state set to null
*/
public GenHolder() {
heldValue = null;
}
/**
* Creates a new holder, with its state initialized to the provided
* value
*
* @param held
* The state to initialize this holder to.
*/
public GenHolder(T held) {
heldValue = held;
}
/*
* (non-Javadoc)
*
* @see bjc.utils.data.IHolder#doWith(java.util.function.Consumer)
*/
@Override
public void doWith(Consumer<T> action) {
if (action == null) {
throw new NullPointerException("Action must be non-null");
}
action.accept(heldValue);
}
/*
* (non-Javadoc)
*
* @see bjc.utils.data.IHolder#map(java.util.function.Function)
*/
@Override
public <NewT> IHolder<NewT> map(Function<T, NewT> transformer) {
if (transformer == null) {
throw new NullPointerException("Transformer must be non-null");
}
return new GenHolder<>(transformer.apply(heldValue));
}
/*
* (non-Javadoc)
*
* @see bjc.utils.data.IHolder#transform(java.util.function.Function)
*/
@Override
public IHolder<T> transform(Function<T, T> transformer) {
if (transformer == null) {
throw new NullPointerException("Transformer must be non-null");
}
heldValue = transformer.apply(heldValue);
return this;
}
/*
* (non-Javadoc)
*
* @see bjc.utils.data.IHolder#unwrap(java.util.function.Function)
*/
@Override
public <E> E unwrap(Function<T, E> unwrapper) {
if (unwrapper == null) {
throw new NullPointerException("Unwrapper must be null");
}
return unwrapper.apply(heldValue);
}
@Override
public String toString() {
if (heldValue == null) {
return "(null)";
}
return heldValue.toString();
}
}
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