Add a helper class

src/main/java/org/leolo/nrdatad/util/Range.java

@@ -0,0 +1,25 @@
+package org.leolo.nrdatad.util;
+
+public class Range<E extends Comparable> {
+
+    private E lowerBound;
+    private E upperBound;
+
+    public Range(E bound1, E bound2){
+        if(bound1.compareTo(bound2)==-1){
+            lowerBound = bound1;
+            upperBound = bound2;
+        }else{
+            lowerBound = bound2;
+            upperBound = bound1;
+        }
+    }
+
+    public E getLowerBound() {
+        return lowerBound;
+    }
+
+    public E getUpperBound() {
+        return upperBound;
+    }
+}

src/test/java/org/leolo/nrdatad/util/RangeTest.java

@@ -0,0 +1,20 @@
+package org.leolo.nrdatad.util;
+
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+public class RangeTest {
+
+    @Test
+    public void basicInteger1(){
+        Range<Integer> range = new Range<>(1,2);
+        assertEquals(1, range.getLowerBound().intValue());
+        assertEquals(2, range.getUpperBound().intValue());
+        range = new Range<>(2,1);
+        assertEquals(1, range.getLowerBound().intValue());
+        assertEquals(2, range.getUpperBound().intValue());
+        range = new Range<>(2,2);
+        assertEquals(2, range.getLowerBound().intValue());
+        assertEquals(2, range.getUpperBound().intValue());
+    }
+}