Add hashCode and equals methods to prism.Pair.

prism/src/prism/Pair.java

@@ -58,6 +58,39 @@ public class Pair<X,Y> implements Entry<X, Y>
 		return second;
 	}
 	
+	@Override
+	public int hashCode()
+	{
+		final int prime = 31;
+		int result = 1;
+		result = prime * result + ((first == null) ? 0 : first.hashCode());
+		result = prime * result + ((second == null) ? 0 : second.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;
+		Pair<?, ?> other = (Pair<?, ?>) obj;
+		if (first == null) {
+			if (other.first != null)
+				return false;
+		} else if (!first.equals(other.first))
+			return false;
+		if (second == null) {
+			if (other.second != null)
+				return false;
+		} else if (!second.equals(other.second))
+			return false;
+		return true;
+	}
+	
 	@Override
 	public String toString()
 	{