Add chapters 18-20 for the java book

Java-Kompendium/kap18/2/Eingabe.java

@@ -0,0 +1,32 @@
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.io.IOException;
+import java.util.ArrayList;
+
+public class Eingabe extends Thread {
+    private Personal personal;
+
+    public Eingabe(Personal personal) {
+        this.personal = personal;
+    }
+
+    @Override
+    public void run() {
+        boolean weiter = true;
+
+        while (weiter) {
+            synchronized(this.personal) {
+                try {
+                    var inputStream = new InputStreamReader(System.in);
+                    var bufferedReader = new BufferedReader(inputStream);
+
+                    this.personal.eingabe();
+
+                    System.out.println("Weitere Berechnung durchführen (j/n)?");
+                    weiter = bufferedReader.readLine().equals("j");
+                } catch (IOException exception) {
+                }
+            }
+        }
+    }
+}