make heap type an enum

src/main/java/BiGpairSEQ.java

@@ -13,9 +13,9 @@ public class BiGpairSEQ {
     private static boolean cacheCells = false;
     private static boolean cachePlate = false;
     private static boolean cacheGraph = false;
-    private static String priorityQueueHeapType = "FIBONACCI";
-    private static boolean outputBinary = true;
-    private static boolean outputGraphML = false;
+    private static HeapType priorityQueueHeapType = HeapType.FIBONACCI;
+    private static boolean outputBinary = false;
+    private static boolean outputGraphML = true;
 
     public static void main(String[] args) {
         if (args.length == 0) {
@@ -156,15 +156,15 @@ public class BiGpairSEQ {
     }
 
     public static String getPriorityQueueHeapType() {
-        return priorityQueueHeapType;
+        return priorityQueueHeapType.name();
     }
 
     public static void setPairingHeap() {
-        priorityQueueHeapType = "PAIRING";
+        priorityQueueHeapType = HeapType.PAIRING;
     }
 
     public static void setFibonacciHeap() {
-        priorityQueueHeapType = "FIBONACCI";
+        priorityQueueHeapType = HeapType.FIBONACCI;
     }
 
     public static boolean outputBinary() {return outputBinary;}

src/main/java/HeapType.java

@@ -0,0 +1,4 @@
+public enum HeapType {
+    FIBONACCI,
+    PAIRING
+}