net.didion.jwnl.data.relationship.Relationship Maven / Gradle / Ivy

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/**
 * Java WordNet Library (JWNL)
 * See the documentation for copyright information.
 */
package net.didion.jwnl.data.relationship;

import net.didion.jwnl.data.PointerTarget;
import net.didion.jwnl.data.PointerType;
import net.didion.jwnl.data.Synset;
import net.didion.jwnl.data.list.PointerTargetNode;
import net.didion.jwnl.data.list.PointerTargetNodeList;

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.StringWriter;

/**
 * A Relationship encapsulates the relationship between two synsets. Basically, it is a list of
 * synsets/words that one must traverse to get from the source synset to the target synset of the
 * relationship, for some relationship type.
 * 
 * There are two types of relationships - {@link net.didion.jwnl.data.relationship.SymmetricRelationship Symmetric}
 * and {@link net.didion.jwnl.data.relationship.AsymmetricRelationship Asymmetric}.
 */
public abstract class Relationship {
	/** The nodes that comprise the relationship. */
	private PointerTargetNodeList _nodes;
	/** The relationship's type */
	private PointerType _type;

	private Synset _sourceSynset;
	private Synset _targetSynset;

	protected Relationship(PointerType type, PointerTargetNodeList nodes, Synset sourceSynset, Synset targetSynset) {
		_type = type;
		_nodes = nodes;
		_sourceSynset = sourceSynset;
		_targetSynset = targetSynset;
	}

	public abstract Relationship reverse();

	/** Get the list that contains the nodes of this relationship.*/
	public PointerTargetNodeList getNodeList() {
		return _nodes;
	}

	/** Get the pointer target of the source node. */
	public PointerTarget getSourcePointerTarget() {
		return ((PointerTargetNode) _nodes.get(0)).getPointerTarget();
	}

	/** Get the pointer target of the target node. */
	public PointerTarget getTargetPointerTarget() {
		return ((PointerTargetNode) _nodes.get(_nodes.size() - 1)).getPointerTarget();
	}

	public String toString() {
		StringBufferOutputStream stream = new StringBufferOutputStream();
		_nodes.print(new PrintStream(stream));
		return stream.getStringBuffer().toString();
	}

	/** Two relationships are assumed equal if they have the same source synset, target synset, and type */
	public boolean equals(Object obj) {
		if (obj instanceof Relationship) {
			Relationship r = (Relationship) obj;
			return r.getType().equals(getType())
			    && r.getSourceSynset().equals(getSourceSynset())
			    && r.getTargetSynset().equals(getTargetSynset());
		}
		return false;
	}

	public PointerType getType() {
		return _type;
	}

	/** Get the Synset that is the source of this relationship.*/
	public Synset getSourceSynset() {
		return _sourceSynset;
	}

	/** Get the Synset that is the target of this relationship. */
	public Synset getTargetSynset() {
		return _targetSynset;
	}

	public int getSize() {
		return getNodeList().size();
	}

	/**
	 * Get the depth of this relationship. Depth is a concept that can be defined by each relationship type.
	 * The default notion of depth is the number of pointers that need to be traversed to go from the source
	 * to target synset. This is basically getSize() - 1.
	 */
	public int getDepth() {
		return getSize() - 1;
	}

	private static class StringBufferOutputStream extends OutputStream {
		private StringWriter writer = new StringWriter();

		public void write(int b) throws IOException {
			writer.write(b);
		}

		public StringBuffer getStringBuffer() {
			return writer.getBuffer();
		}
	}
}