Refactor builder

There was some code duplication and unclear call delegation between
methods of similar names.

Author: damianmalczewski

src/main/java/io/github/problem4j/core/AbstractProblemBuilder.java

@@ -20,17 +20,14 @@
  */
 package io.github.problem4j.core;
 
-import io.github.problem4j.core.Problem.Extension;
 import java.io.Serializable;
 import java.net.URI;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Objects;
 import java.util.Optional;
-import java.util.stream.Stream;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -213,10 +210,12 @@ public ProblemBuilder extensions(@Nullable Map<String, @Nullable Object> extensi
    */
   @Override
   public ProblemBuilder extensions(Problem.@Nullable Extension @Nullable ... extensions) {
-    if (extensions != null && extensions.length > 0) {
-      Stream.of(extensions)
-          .filter(AbstractProblemBuilder::isExtensionValid)
-          .forEach(e -> this.extensions.put(e.getKey(), Objects.requireNonNull(e.getValue())));
+    if (extensions != null) {
+      for (Problem.@Nullable Extension e : extensions) {
+        if (e != null && e.getValue() != null) {
+          this.extensions.put(e.getKey(), e.getValue());
+        }
+      }
     }
     return this;
   }
@@ -231,9 +230,7 @@ public ProblemBuilder extensions(Problem.@Nullable Extension @Nullable ... exten
   public ProblemBuilder extensions(
       @Nullable Collection<? extends Problem.@Nullable Extension> extensions) {
     if (extensions != null && !extensions.isEmpty()) {
-      extensions.stream()
-          .filter(AbstractProblemBuilder::isExtensionValid)
-          .forEach(e -> this.extensions.put(e.getKey(), Objects.requireNonNull(e.getValue())));
+      extensions(extensions.toArray(new Problem.Extension[0]));
     }
     return this;
   }
@@ -300,8 +297,4 @@ public String toString() {
 
     return "ProblemBuilder{" + String.join(", ", entries) + "}";
   }
-
-  private static boolean isExtensionValid(@Nullable Extension extension) {
-    return extension != null && extension.getValue() != null;
-  }
 }

src/main/java/io/github/problem4j/core/Problem.java

@@ -74,6 +74,8 @@ static ProblemBuilder builder() {
    * @throws IllegalArgumentException if the {@code key} is {@code null}
    */
   static Extension extension(@Nullable String key, @Nullable Object value) {
+    // with JSpecify, the nullability check might not be necessary, kept to not break existing
+    // behavior, may be revisited in future major versions
     if (key == null) {
       throw new IllegalArgumentException("key cannot be null");
     }

src/main/java/io/github/problem4j/core/ProblemBuilder.java

@@ -123,7 +123,10 @@ public interface ProblemBuilder {
    * @return this builder instance for chaining
    */
   default ProblemBuilder extension(Problem.@Nullable Extension extension) {
-    return extensions(extension);
+    if (extension != null) {
+      return extension(extension.getKey(), extension.getValue());
+    }
+    return this;
   }
 
   /**

src/test/java/io/github/problem4j/core/ProblemImplTest.java

@@ -139,7 +139,7 @@ void givenSameProblems_shouldBeEqual() {
     Object problem;
     Object other;
 
-    problem = other = new ProblemImpl( "title", 404, "detail", mapOf("key", "value"));
+    problem = other = new ProblemImpl("title", 404, "detail", mapOf("key", "value"));
 
     assertThat(problem).isEqualTo(other);
   }
@@ -154,26 +154,24 @@ void givenTwoDifferentProblems_shouldNotBeEqual() {
 
   @Test
   void givenProblemAndDifferentObject_shouldNotBeEqual() {
-    Object problem = new ProblemImpl( "title1", 404, "detail1",  mapOf("key", "value"));
+    Object problem = new ProblemImpl("title1", 404, "detail1", mapOf("key", "value"));
     Object differentObject = "always wanted to be a problem";
 
     assertThat(problem).isNotEqualTo(differentObject);
   }
 
   @Test
   void givenTwoEqualProblems_shouldHaveSameHashCode() {
-    Problem problem1 = new ProblemImpl( "title", 404, "detail",  mapOf("key", "value"));
-    Problem problem2 = new ProblemImpl( "title", 404, "detail",  mapOf("key", "value"));
+    Problem problem1 = new ProblemImpl("title", 404, "detail", mapOf("key", "value"));
+    Problem problem2 = new ProblemImpl("title", 404, "detail", mapOf("key", "value"));
 
     assertThat(problem1.hashCode()).isEqualTo(problem2.hashCode());
   }
 
   @Test
   void givenTwoDifferentProblems_shouldHaveDifferentHashCodes() {
-    Problem problem1 =
-        new ProblemImpl( "title1", 404, "detail1",  mapOf("key", "value1"));
-    Problem problem2 =
-        new ProblemImpl( "title2", 500, "detail2",  mapOf("key", "value2"));
+    Problem problem1 = new ProblemImpl("title1", 404, "detail1", mapOf("key", "value1"));
+    Problem problem2 = new ProblemImpl("title2", 500, "detail2", mapOf("key", "value2"));
 
     assertThat(problem1.hashCode()).isNotEqualTo(problem2.hashCode());
   }