making this Java 1.7 compatible

Author: hannes

pom.xml

@@ -84,8 +84,8 @@
         <artifactId>maven-compiler-plugin</artifactId>
         <version>3.5.1</version>
         <configuration>
-          <source>1.8</source>
-          <target>1.8</target>
+          <source>1.7</source>
+          <target>1.7</target>
         </configuration>
       </plugin>
 	<plugin>

src/main/java/ldbc/snb/datagen/util/FactorTable.java

@@ -304,7 +304,12 @@ public void writePersonFactors(OutputStream writer ) {
             }
             Map<Integer,String> medianNames = new TreeMap<Integer,String>();
             for (Map.Entry<Integer,List<String>> entry : countryNames.entrySet()) {
-                entry.getValue().sort( (a ,b) -> a.compareTo(b));
+                entry.getValue().sort(new Comparator<String>(){
+                    @Override
+                    public int compare(String o1, String o2) {
+                        return o1.compareTo(o2);
+                    }
+                });
                 medianNames.put(entry.getKey(),entry.getValue().get(entry.getValue().size()/2));
             }
             for (Map.Entry<Long, PersonCounts> c: personCounts_.entrySet()){