diff --git a/src/org/eidecker/oca8lernen/general/CalendarAPI.java b/src/org/eidecker/oca8lernen/general/CalendarAPI.java
new file mode 100644
index 0000000..dab4fba
--- /dev/null
+++ b/src/org/eidecker/oca8lernen/general/CalendarAPI.java
@@ -0,0 +1,67 @@
+package org.eidecker.oca8lernen.general;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.LocalTime;
+import java.time.Month;
+import java.time.format.DateTimeFormatter;
+import java.time.format.FormatStyle;
+import java.time.temporal.UnsupportedTemporalTypeException;
+import org.junit.jupiter.api.Test;
+
+public class CalendarAPI {
+
+	@Test
+	public void testCalendarAPI() {
+		LocalDate date = LocalDate.of(2020, Month.APRIL, 3);
+		LocalTime time = LocalTime.of(12, 45);
+		LocalDateTime dateTime = LocalDateTime.of(date, time);
+
+		DateTimeFormatter dateFormatter = DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM);
+		DateTimeFormatter timeFormatter = DateTimeFormatter.ofLocalizedTime(FormatStyle.MEDIUM);
+		DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.MEDIUM);
+
+		System.out.println(dateFormatter.format(date));
+		System.out.println(timeFormatter.format(time));
+		System.out.println(dateTimeFormatter.format(dateTime));
+
+		DateTimeFormatter myOwnFormatter = DateTimeFormatter.ofPattern("MM d yyyy, HH:mm");
+		System.out.println(myOwnFormatter.format(dateTime));
+
+		assertThrows(UnsupportedTemporalTypeException.class, () -> {
+			dateTimeFormatter.format(time);
+		});
+
+		assertThrows(UnsupportedTemporalTypeException.class, () -> {
+			myOwnFormatter.format(time);
+		});
+
+	}
+
+	@Test
+	public void parseDates() {
+		DateTimeFormatter timeFormatter = DateTimeFormatter.ofPattern("HH:mm");
+		DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyMMddHHmm");
+
+		LocalTime localTime = LocalTime.parse("23:11", timeFormatter);
+		localTime = LocalTime.parse("1901221209", dateTimeFormatter);
+
+
+		LocalDateTime dateTime;
+		dateTime = LocalDateTime.parse("1908221132", dateTimeFormatter);
+
+
+	}
+
+	@Test
+	public void testTheImpossible() {
+
+//		LocalDate date = new LocalDate();
+
+	}
+
+
+
+}
diff --git a/src/org/eidecker/oca8lernen/general/KLassenInitialisierung.java b/src/org/eidecker/oca8lernen/general/KLassenInitialisierung.java
index 6ac7fff..56a2944 100644
--- a/src/org/eidecker/oca8lernen/general/KLassenInitialisierung.java
+++ b/src/org/eidecker/oca8lernen/general/KLassenInitialisierung.java
@@ -27,11 +27,16 @@ public class KLassenInitialisierung {
 class Oberklasse {
 
 	static {
-		System.out.println("Oberklasse statischer Initialisierungsblock");
+		synchronized (Oberklasse.class) {
+			System.out.println("Oberklasse statischer Initialisierungsblock");
+		}
+
 	}
 
 	{
-		System.out.println("Oberklasse Initialisierungsblock");
+		synchronized (this) {
+			System.out.println("Oberklasse Initialisierungsblock");
+		}
 	}
 
 
diff --git a/src/org/eidecker/oca8lernen/general/ValidIdentifier.java b/src/org/eidecker/oca8lernen/general/ValidIdentifier.java
new file mode 100644
index 0000000..441cc33
--- /dev/null
+++ b/src/org/eidecker/oca8lernen/general/ValidIdentifier.java
@@ -0,0 +1,13 @@
+package org.eidecker.oca8lernen.general;
+
+public class ValidIdentifier {
+
+	class $ {
+
+		String H1;
+
+	}
+
+
+
+}