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edu.stanford.nlp.util.Pair Maven / Gradle / Ivy
package edu.stanford.nlp.util;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.Serializable;
import java.util.Comparator;
import java.util.List;
import edu.stanford.nlp.util.logging.PrettyLoggable;
import edu.stanford.nlp.util.logging.PrettyLogger;
import edu.stanford.nlp.util.logging.Redwood.RedwoodChannels;
/**
* Pair is a Class for holding mutable pairs of objects.
*
* Implementation note:
* on a 32-bit JVM uses ~ 8 (this) + 4 (first) + 4 (second) = 16 bytes.
* on a 64-bit JVM uses ~ 16 (this) + 8 (first) + 8 (second) = 32 bytes.
*
* Many applications use a lot of Pairs so it's good to keep this
* number small.
*
* @author Dan Klein
* @author Christopher Manning (added stuff from Kristina's, rounded out)
* @version 2002/08/25
*/
public class Pair implements Comparable>, Serializable, PrettyLoggable {
/**
* Direct access is deprecated. Use first().
*
* @serial
*/
public T1 first;
/**
* Direct access is deprecated. Use second().
*
* @serial
*/
public T2 second;
public Pair() {
// first = null; second = null; -- default initialization
}
public Pair(T1 first, T2 second) {
this.first = first;
this.second = second;
}
public T1 first() {
return first;
}
public T2 second() {
return second;
}
public void setFirst(T1 o) {
first = o;
}
public void setSecond(T2 o) {
second = o;
}
@Override
public String toString() {
return "(" + first + "," + second + ")";
}
@Override
public boolean equals(Object o) {
if (o instanceof Pair) {
@SuppressWarnings("rawtypes")
Pair p = (Pair) o;
return (first == null ? p.first() == null : first.equals(p.first())) && (second == null ? p.second() == null : second.equals(p.second()));
} else {
return false;
}
}
@Override
public int hashCode() {
int firstHash = (first == null ? 0 : first.hashCode());
int secondHash = (second == null ? 0 : second.hashCode());
return firstHash*31 + secondHash;
}
public List asList() {
return CollectionUtils.makeList(first, second);
}
/**
* Read a string representation of a Pair from a DataStream.
* This might not work correctly unless the pair of objects are of type
* String.
*/
public static Pair readStringPair(DataInputStream in) {
Pair p = new Pair<>();
try {
p.first = in.readUTF();
p.second = in.readUTF();
} catch (Exception e) {
e.printStackTrace();
}
return p;
}
/**
* Returns a Pair constructed from X and Y. Convenience method; the
* compiler will disambiguate the classes used for you so that you
* don't have to write out potentially long class names.
*/
public static Pair makePair(X x, Y y) {
return new Pair<>(x, y);
}
/**
* Write a string representation of a Pair to a DataStream.
* The toString() method is called on each of the pair
* of objects and a String representation is written.
* This might not allow one to recover the pair of objects unless they
* are of type String.
*/
public void save(DataOutputStream out) {
try {
out.writeUTF(first.toString());
out.writeUTF(second.toString());
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* Compares this Pair to another object.
* If the object is a Pair, this function will work providing
* the elements of the Pair are themselves comparable.
* It will then return a value based on the pair of objects, where
* p > q iff p.first() > q.first() ||
* (p.first().equals(q.first()) && p.second() > q.second()).
* If the other object is not a Pair, it throws a
* ClassCastException.
*
* @param another the Object to be compared.
* @return the value 0 if the argument is a
* Pair equal to this Pair; a value less than
* 0 if the argument is a Pair
* greater than this Pair; and a value
* greater than 0 if the argument is a
* Pair less than this Pair.
* @throws ClassCastException if the argument is not a
* Pair.
* @see java.lang.Comparable
*/
@SuppressWarnings("unchecked")
public int compareTo(Pair another) {
if (first() instanceof Comparable) {
int comp = ((Comparable) first()).compareTo(another.first());
if (comp != 0) {
return comp;
}
}
if (second() instanceof Comparable) {
return ((Comparable) second()).compareTo(another.second());
}
if ((!(first() instanceof Comparable)) && (!(second() instanceof Comparable))) {
throw new AssertionError("Neither element of pair comparable");
}
return 0;
}
/**
* If first and second are Strings, then this returns an MutableInternedPair
* where the Strings have been interned, and if this Pair is serialized
* and then deserialized, first and second are interned upon
* deserialization.
*
* @param p A pair of Strings
* @return MutableInternedPair, with same first and second as this.
*/
public static Pair stringIntern(Pair p) {
return new MutableInternedPair(p);
}
/**
* Returns an MutableInternedPair where the Strings have been interned.
* This is a factory method for creating an
* MutableInternedPair. It requires the arguments to be Strings.
* If this Pair is serialized
* and then deserialized, first and second are interned upon
* deserialization.
* Note: I put this in thinking that its use might be
* faster than calling x = new Pair(a, b).stringIntern()
* but it's not really clear whether this is true.
*
* @param first The first object
* @param second The second object
* @return An MutableInternedPair, with given first and second
*/
public static Pair internedStringPair(String first, String second) {
return new MutableInternedPair(first, second);
}
/**
* use serialVersionUID for cross version serialization compatibility
*/
private static final long serialVersionUID = 1360822168806852921L;
static class MutableInternedPair extends Pair {
private MutableInternedPair(Pair p) {
super(p.first, p.second);
internStrings();
}
private MutableInternedPair(String first, String second) {
super(first, second);
internStrings();
}
protected Object readResolve() {
internStrings();
return this;
}
private void internStrings() {
if (first != null) {
first = first.intern();
}
if (second != null) {
second = second.intern();
}
}
// use serialVersionUID for cross version serialization compatibility
private static final long serialVersionUID = 1360822168806852922L;
}
/**
* {@inheritDoc}
*/
public void prettyLog(RedwoodChannels channels, String description) {
PrettyLogger.log(channels, description, this.asList());
}
/**
* Compares a Pair to another Pair according to the first object of the pair only
* This function will work providing
* the first element of the Pair is comparable, otherwise will throw a
* ClassCastException
* @author jonathanberant
*
* @param
* @param
*/
public static class ByFirstPairComparator implements Comparator> {
@SuppressWarnings("unchecked")
@Override
public int compare(Pair pair1, Pair pair2) {
return ((Comparable) pair1.first()).compareTo(pair2.first());
}
}
/**
* Compares a Pair to another Pair according to the first object of the pair only in decreasing order
* This function will work providing
* the first element of the Pair is comparable, otherwise will throw a
* ClassCastException
* @author jonathanberant
*
* @param
* @param
*/
public static class ByFirstReversePairComparator implements Comparator> {
@SuppressWarnings("unchecked")
@Override
public int compare(Pair pair1, Pair pair2) {
return -((Comparable) pair1.first()).compareTo(pair2.first());
}
}
/**
* Compares a Pair to another Pair according to the second object of the pair only
* This function will work providing
* the first element of the Pair is comparable, otherwise will throw a
* ClassCastException
* @author jonathanberant
*
* @param
* @param
*/
public static class BySecondPairComparator implements Comparator> {
@SuppressWarnings("unchecked")
@Override
public int compare(Pair pair1, Pair pair2) {
return ((Comparable) pair1.second()).compareTo(pair2.second());
}
}
/**
* Compares a Pair to another Pair according to the second object of the pair only in decreasing order
* This function will work providing
* the first element of the Pair is comparable, otherwise will throw a
* ClassCastException
* @author jonathanberant
*
* @param
* @param
*/
public static class BySecondReversePairComparator implements Comparator> {
@SuppressWarnings("unchecked")
@Override
public int compare(Pair pair1, Pair pair2) {
return -((Comparable) pair1.second()).compareTo(pair2.second());
}
}
}
