Created new project for numbers and moved source as per the review

java-numbers-3/src/main/java/com/baeldung/doubletolong/DoubleToLongUnitTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.doubletolong;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class DoubleToLongUnitTest {
+
+    final static double VALUE = 9999.999;
+
+    @Test
+    public void using_longValue() {
+        Assert.assertEquals(9999L, Double.valueOf(VALUE)
+            .longValue());
+    }
+
+    @Test
+    public void using_Math_Round() {
+        Assert.assertEquals(10000L, Math.round(VALUE));
+    }
+
+    @Test
+    public void using_Math_Ceil() {
+        Assert.assertEquals(10000L, Math.ceil(VALUE), 0);
+    }
+
+    @Test
+    public void using_Math_Floor() {
+        Assert.assertEquals(9999L, Math.floor(VALUE), 0);
+    }
+
+    @Test
+    public void using_Type_Cast() {
+        Assert.assertEquals(9999L, (long) VALUE);
+    }
+
+}