org.unix4j.unix.head.HeadOptions Maven / Gradle / Ivy
package org.unix4j.unix.head;
import java.util.Collections;
import java.util.Iterator;
import org.unix4j.convert.OptionSetConverters.OptionSetConverter;
import org.unix4j.convert.ValueConverter;
import org.unix4j.option.DefaultOptionSet;
import org.unix4j.option.Option;
import org.unix4j.option.OptionSet;
import org.unix4j.unix.Head;
import org.unix4j.unix.head.HeadOption;
/**
* Interface implemented by all option sets for the {@link Head head} command.
* It is recommended to use {@link Head#Options} to specify a valid
* combination of options.
*
* The options for the head command are:
*
*
* {@code -c} {@code --chars} The {@code count} argument is in units of characters instead of
lines. Starts from 1 and includes line ending characters. {@code -q} {@code --suppressHeaders} Suppresses printing of headers when multiple files are being
examined.
*
* This interface serves as an alias for the extended interface to simplify the
* command signature methods by avoiding generic parameters.
*/
public interface HeadOptions extends OptionSet {
/**
* Constant for an empty option set.
*/
HeadOptions EMPTY = new HeadOptions() {
@Override
public Class optionType() {
return HeadOption.class;
}
@Override
public boolean isSet(HeadOption option) {
return false;
}
/**
* Returns 0 as this is a set with no active options.
*
* @return zero
*/
@Override
public int size() {
return 0;
}
/**
* Returns an immutable empty set.
*
* @return an immutable empty set.
*/
@Override
public java.util.Set asSet() {
return Collections.emptySet();
}
/**
* Returns an iterator returning no elements.
*
* @return an immutable iterator with no elements.
*/
@Override
public Iterator iterator() {
return asSet().iterator();
}
/**
* Returns true if the {@link Option#acronym() acronym} should be used
* for the specified {@code option} in string representations.
*
* This method returns always true;
*
* @param option
* the option of interest
* @return always true
*/
@Override
public boolean useAcronymFor(HeadOption option) {
return true;
}
};
/**
* Default implementation for a modifiable option set.
*/
class Default extends DefaultOptionSet implements HeadOptions {
/**
* Default constructor for an empty option set with no active options.
*/
public Default() {
super(HeadOption.class);
}
/**
* Constructor for an option set with a single active option.
* @param option the option to be set
*/
public Default(HeadOption option) {
super(option);
}
/**
* Constructor for an option set with the given active options.
* @param options the options to be set
*/
public Default(HeadOption... options) {
this();
setAll(options);
}
/**
* Constructor for an option set initialized with the options given by
* another option set.
*
* @param optionSet set with the options to be active
*/
public Default(OptionSet optionSet) {
this();
setAll(optionSet);
}
}
/**
* Value converter for {@link HeadOptions} based on an {@link OptionSetConverter}.
*/
ValueConverter CONVERTER = new ValueConverter() {
private final OptionSetConverter converter = new OptionSetConverter(HeadOption.class);
@Override
public HeadOptions convert(Object value) {
final OptionSet set = converter.convert(value);
return set == null ? null : new Default(set);
}
};
}