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    • dcutils.tuples.Pair Maven / Gradle / Ivy

    package dcutils.tuples;

// Import Java JDK Classes
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;

/**
 * Contains exactly two items.
    
 * @author dca
 */
public class Pair implements Iterable, Comparator {
   /** The first item of the pair.
     */
   private A first;

   /** The second item of the pair.
     */
   private B second;

   /**
    * The constructor initializes the items of the pair.
    
    * @param first The first item of the pair.
    
    * @param second The second item of the pair.
    
    */
   public Pair(A first, B second) {
      first(first);
      second(second);
   } // END constructor

   /**
    * The getter for the first item.
    
    * Returns the first item of the pair.
    
    * @return first The first item of the pair.
    
    */
   public A first() {
      return first;
   } // END first

   /**
    * The setter for the first item.
    
    * Sets the first item of the pair.
    
    * @param first The first item of the pair.
    
    * @return this.
    
    */
   public Pair first(A first) {
      this.first = first;
      return this;
   } // END first

   /**
    * The getter for the second item.
    
    * Returns the second item of the pair.
    
    * @return second The second item of the pair.
    
    */
   public B second() {
      return second;
   } // END second

   /**
    * The setter for the second item.
    
    * Sets the second item of the pair.
    
    * @param second The second item of the pair.
    
    * @return this.
    
    */
   public Pair second(B second) {
      this.second = second;
      return this;
   } // END second

   /**
    * Returns the pair information as a tuple.
    
    * The format of the tuple is: [first, second, third].
    
    * If any of the items are null, then the word "null" will be shown in its place.
    
    * @return String A tuple format of the pair.
    
    */
   @Override
   public String toString() {
      return Arrays.toString(toArray());
   } // END toString

   /**
    * Decides if an object is equal to this pair.
    
    * In order for an object to be equal to this pair:
    
    * the object must also be a pair, must not be null, and each of its items must equal this pair's items.
    
    * @param obj The item to check for value equality.
    
    * @return True or false
    
    */
   @Override
   public boolean equals(Object obj) {
      if(null == obj) {
         return false;
      } else if(obj instanceof Pair) {
         Pair pair = (Pair)obj;

         return (
            0 == compare(first,  pair.first()) &&
            0 == compare(second, pair.second())
         );
      } else {
         return false;
      } // END if/else
   } // END equals

   /**
    * Compares two arguments.
    
    * If they are the same, "0" will be returned.
    
    * If they are different, "-1" will be returned.
    
    * This method is used primarily by the equals(Object) method to compare internal fields to those of another Pair.
    
    * @param lhs The left-hand-side argument.
    
    * @param rhs The right-hand-side argument.
    
    * @see #equals(Object)
    */
   @Override
   public int compare(Object lhs, Object rhs) {
      if(null == lhs ^ null == rhs) return -1; // If one or the other are null -> they are not the same.
      else if(null == lhs && null == rhs) return 0; // If both are null -> they are the same.
      else return (lhs.equals(rhs) ? 0 : -1); // If both are defined and equal -> they are the same.
   } // END compare

   /**
    * Creates a hash code for this pair.
    
    * The hash code uses prime numbers and the hash codes of this pair's items.
    
    * @return integer The hash code.
    
    */
   @Override
   public int hashCode() {
      int hashCode = 101;
      for(Object item : this) {
         hashCode = (11 * hashCode) + (null == item ? -1 : item.hashCode());
      } // END loop
      return hashCode;
   } // END hashCode

   /**
    * Returns an iterator over the items in this pair.
    
    * @return The iterator.
    
    */
   @Override
   public Iterator iterator() {
      final List ITEMS = new ArrayList();
      Collections.addAll(ITEMS, toArray());
      return ITEMS.iterator();
   } // END iterator

   /**
    * Creates a new array and defines it with the pair's items.
    
    * @return Object[] The object array of the pair's items.
    
    */
   public Object[] toArray() {
      return new Object[] {first, second};
   } // END toArray
} // END class Pair
    
    
    
    

    




    
    
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