Sort crossRef by order and url

Signed-off-by: Arthit Suriyawongkul <arthit@gmail.com>

Author: bact

src/main/java/org/spdx/storage/listedlicense/LicenseJson.java

@@ -19,6 +19,7 @@
 
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -557,4 +558,14 @@ public List<PropertyDescriptor> getPropertyValueDescriptors() {
 		});
 		return retval;
 	}
+
+	/**
+	 * Sort the crossRef list by order, with URL as a secondary sort key for
+	 * entries with no order set.
+	 */
+	public void sortCrossRef() {
+		crossRef.sort(Comparator
+				.comparingInt((CrossRefJson c) -> c.order != null ? c.order : Integer.MAX_VALUE)
+				.thenComparing(c -> c.url != null ? c.url : ""));
+	}
 }