add subfield helpers

gradle.properties

@@ -1,5 +1,5 @@
 group = org.xbib
 name = marc
-version = 2.9.2
+version = 2.9.3
 
 org.gradle.warning.mode = ALL

src/main/java/org/xbib/marc/MarcField.java

@@ -24,6 +24,8 @@ import java.util.Deque;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.function.BinaryOperator;
+import java.util.function.Supplier;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
@@ -104,6 +106,37 @@ public class MarcField implements Comparable<MarcField> {
         return builder.subfields;
     }
 
+    /**
+     * Return the subfields of this MARC field as Map. Attention: this works only if there are unique subfield IDs.
+     * @return the subfields as map
+     */
+    public Map<String, Object> getSubfieldsAsMap() {
+        return builder.subfields.stream().collect(Collectors.toMap(Subfield::getId, Subfield::getValue));
+    }
+
+    /**
+     * Return the subfields of this MARC field as Map. Attention: this works only if there are unique subfield IDs.
+     * @param mergeFunction the merge function
+     * @param supplier the supplier
+     * @return the subfields as map
+     */
+    public Map<String, Object> getSubfieldsAsMap(BinaryOperator<Object> mergeFunction, Supplier<Map<String, Object>> supplier) {
+        return builder.subfields.stream().collect(Collectors.toMap(Subfield::getId, Subfield::getValue,
+                mergeFunction, supplier));
+    }
+
+    /**
+     * Collect subfield values of a specified collection of subfield IDs.
+     * @param subfieldIds the given collection of subfield IDs
+     * @return the list of subfield values
+     */
+    public List<String> getSubfieldValues(Collection<String> subfieldIds) {
+        return builder.subfields.stream()
+                .filter(subfield -> subfieldIds.contains(subfield.getId()))
+                .map(Subfield::getValue)
+                .collect(Collectors.toList());
+    }
+
     /**
      * Return all subfields of a given subfield ID. Multiple occurences may occur.
      * @param subfieldId subfield ID