Make this into a proper value class.

src/main/java/com/samskivert/depot/Tuple2.java

@@ -22,16 +22,28 @@ package com.samskivert.depot;
 
 import java.io.Serializable;
 
-import com.samskivert.depot.impl.QueryResult;
+import com.google.common.base.Objects;
 
 /**
- * Contains a two column result.
+ * Contains a two column result. This class is immutable and the objects it references are also
+ * meant to be immutable. They will generally contain only Depot primitive types (Java primitives,
+ * SQL primitives and some array types), which should be treated as immutable.
  */
 public class Tuple2<A,B> implements Serializable
 {
+    /** The first column of the result. */
     public final A a;
+
+    /** The second column of the result. */
     public final B b;
 
+    /** Constructs an initialized two tuple. */
+    public static <A, B> Tuple2<A, B> newTuple (A a, B b)
+    {
+        return new Tuple2<A, B>(a, b);
+    }
+
+    /** Constructs an initialized two tuple. */
     public Tuple2 (A a, B b)
     {
         this.a = a;
@@ -43,4 +55,21 @@ public class Tuple2<A,B> implements Serializable
     {
         return "[" + a + "," + b + "]";
     }
+
+    @Override
+    public int hashCode ()
+    {
+        return Objects.hashCode(a, b);
+    }
+
+    @Override
+    public boolean equals (Object other)
+    {
+        if (other instanceof Tuple2<?,?>) {
+            Tuple2<?,?> otup = (Tuple2<?,?>)other;
+            return Objects.equal(a, otup.a) && Objects.equal(b, otup.b);
+        } else {
+            return false;
+        }
+    }
 }