Add Java-Kompendium book

Java-Kompendium/kap5/Task2.java

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+import java.io.*;
+
+public class Task2 {
+    public static void main(String[] args) throws IOException {
+        System.out.print("Geben Sie eine Zahl ein: ");
+
+        var inputStream = new InputStreamReader(System.in);
+        var bufferedStream = new BufferedReader(inputStream);
+
+        String variable = bufferedStream.readLine();
+        int converted = Integer.parseInt(variable);
+
+        System.out.println("Der doppelte Wert ist: " + (converted * 2));
+    }
+}