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package bjc.utils.data;
import java.util.function.Function;
import java.util.function.UnaryOperator;
/**
* A holder that may or may not contain a value
*
* @author ben
*
* @param <ContainedType>
* The type of the value that may or may not be held
*/
public class Option<ContainedType> implements IHolder<ContainedType> {
private ContainedType held;
/**
* Create a new optional, using the given initial value
*
* @param seed
* The initial value for the optional
*/
public Option(ContainedType seed) {
held = seed;
}
@Override
public <BoundType> IHolder<BoundType> bind(Function<ContainedType, IHolder<BoundType>> binder) {
if(held == null) return new Option<>(null);
return binder.apply(held);
}
@Override
public <NewType> Function<ContainedType, IHolder<NewType>> lift(Function<ContainedType, NewType> func) {
return (val) -> {
return new Option<>(func.apply(val));
};
}
@Override
public <MappedType> IHolder<MappedType> map(Function<ContainedType, MappedType> mapper) {
if(held == null) return new Option<>(null);
return new Option<>(mapper.apply(held));
}
@Override
public IHolder<ContainedType> transform(UnaryOperator<ContainedType> transformer) {
if(held != null) {
held = transformer.apply(held);
}
return this;
}
@Override
public <UnwrappedType> UnwrappedType unwrap(Function<ContainedType, UnwrappedType> unwrapper) {
if(held == null) return null;
return unwrapper.apply(held);
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append("Option [");
if(held != null) {
builder.append("held=");
builder.append(held);
}
builder.append("]");
return builder.toString();
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((held == null) ? 0 : held.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if(this == obj) return true;
if(obj == null) return false;
if(getClass() != obj.getClass()) return false;
Option<?> other = (Option<?>) obj;
if(held == null) {
if(other.held != null) return false;
} else if(!held.equals(other.held)) return false;
return true;
}
}
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