Add hasType method

Author: damianmalczewski

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

@@ -3,6 +3,7 @@
 import java.io.Serializable;
 import java.net.URI;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 
 /**
@@ -120,6 +121,16 @@ static Extension extension(String key, Object value) {
    */
   ProblemBuilder toBuilder();
 
+  /**
+   * A convenience method to verify if {@code type} field was assigned, as {@link #BLANK_TYPE} also
+   * mean that type is unassigned.
+   *
+   * @return {@code true} if {@code type} is assigned to a non-blank value, {@code false} otherwise
+   */
+  default boolean hasType() {
+    return getType() != null && !Objects.equals(getType(), BLANK_TYPE);
+  }
+
   /** Represents a single key-value extension in a {@link Problem}. */
   interface Extension extends Map.Entry<String, Object> {
 

src/test/java/io/github/malczuuu/problem4j/core/ProblemBuilderImplTests.java

@@ -25,13 +25,31 @@ void givenNullURIType_shouldNotSetIt() {
     Problem problem = Problem.builder().type((URI) null).build();
 
     assertThat(problem.getType()).isEqualTo(Problem.BLANK_TYPE);
+    assertThat(problem.hasType()).isFalse();
   }
 
   @Test
   void givenNullStringType_shouldNotSetIt() {
     Problem problem = Problem.builder().type((String) null).build();
 
     assertThat(problem.getType()).isEqualTo(Problem.BLANK_TYPE);
+    assertThat(problem.hasType()).isFalse();
+  }
+
+  @Test
+  void givenBlankURIType_shouldNotSetIt() {
+    Problem problem = Problem.builder().type(Problem.BLANK_TYPE).build();
+
+    assertThat(problem.getType()).isEqualTo(Problem.BLANK_TYPE);
+    assertThat(problem.hasType()).isFalse();
+  }
+
+  @Test
+  void givenBlankStringType_shouldNotSetIt() {
+    Problem problem = Problem.builder().type(Problem.BLANK_TYPE.toString()).build();
+
+    assertThat(problem.getType()).isEqualTo(Problem.BLANK_TYPE);
+    assertThat(problem.hasType()).isFalse();
   }
 
   @Test