gigasecond: standardize starter implementation

exercises/gigasecond/src/example/java/Gigasecond.java

@@ -1,19 +1,20 @@
 import java.time.LocalDateTime;
 import java.time.LocalDate;
 
-public class Gigasecond {
+class Gigasecond {
 
-    private LocalDateTime birthDateTime;
+    private LocalDateTime initialDateTime;
 
-    public Gigasecond(LocalDateTime birthDateTime) {
-        this.birthDateTime = birthDateTime;
+    Gigasecond(LocalDate initialDate) {
+        this.initialDateTime = initialDate.atTime(0, 0);
     }
 
-    public Gigasecond(LocalDate birthDate) {
-        this.birthDateTime = birthDate.atTime(0, 0);
+    Gigasecond(LocalDateTime initialDateTime) {
+        this.initialDateTime = initialDateTime;
     }
 
-    public LocalDateTime getDate() {
-        return birthDateTime.plusSeconds(1000000000);
+    LocalDateTime getDate() {
+        return initialDateTime.plusSeconds(1000000000);
     }
+
 }

exercises/gigasecond/src/main/java/Gigasecond.java

@@ -0,0 +1,18 @@
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+
+class Gigasecond {
+
+    Gigasecond(LocalDate initialDate) {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+    }
+
+    Gigasecond(LocalDateTime initialDateTime) {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+    }
+
+    LocalDateTime getDate() {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+    }
+
+}

exercises/gigasecond/src/test/java/GigasecondTest.java

@@ -9,7 +9,6 @@ import static org.junit.Assert.assertEquals;
 
 public class GigasecondTest {
 
-
     @Test
     public void modernTime() {
         Gigasecond gigaSecond = new Gigasecond(LocalDate.of(2011, Month.APRIL, 25));