Github user stain commented on a diff in the pull request:
https://github.com/apache/incubator-commonsrdf/pull/26#discussion_r85510434
--- Diff: api/src/main/java/org/apache/commons/rdf/api/Quad.java ---
@@ -17,16 +17,30 @@
*/
package org.apache.commons.rdf.api;
+import java.util.List;
+import java.util.Map;
import java.util.Objects;
import java.util.Optional;
+import java.util.Set;
/**
* A Quad is a statement in a
* <a href= "http://www.w3.org/TR/rdf11-concepts/#section-dataset"; >RDF-1.1
* Dataset</a>, as defined by
- * <a href= "https://www.w3.org/TR/2014/NOTE-rdf11-datasets-20140225/";
>RDF-1.1
+ * <a href=
"https://www.w3.org/TR/2014/NOTE-rdf11-datasets-20140225/#quad-semantics";
>RDF-1.1
* Concepts and Abstract Syntax</a>, a W3C Working Group Note published on
25
* February 2014.
+ * <p>
+ * A {@link Quad} object in Commons RDF is considered <em>immutable</em>,
that
+ * is, over it's life time it will have consistent behaviour for its
+ * {@link #equals(Object)} and {@link #hashCode()}, and the instances
returned
+ * from {@link #getGraphName()}, {@link #getSubject()}, {@link
#getPredicate()}
+ * and {@link #getObject()} will have consistent {@link
Object#equals(Object)}
+ * behaviour.
+ * <p>
+ * Thus, a {@link Quad} is thread-safe and can be safely used in
collections
--- End diff --
Documenting `Quad` as immutable would indeed prevent any `setSubject()`
bean unless you made them write-once - stringently throwing
`IllegalStateException` until all of them were set.
You could however make such a Java bean from `QuadLike` which don't have
immutability restriction, and then have a `.build()` method or similar that
return the immutable `Quad`.
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