public BinaryTree<String> getBaum1() {
    BinaryTree<String> baum = new BinaryTree<String>(new String("*"));
    baum.getLeftTree().setContent(new String("7"));
    baum.getRightTree().setContent(new String("+"));
    baum.getRightTree().getLeftTree().setContent(new String("8"));
    baum.getRightTree().getRightTree().setContent(new String("-"));
    baum.getRightTree().getRightTree().getLeftTree().setContent(new String("7"));
    baum.getRightTree().getRightTree().getRightTree().setContent(new String("/"));
    baum.getRightTree().getRightTree().getRightTree().getLeftTree().setContent(new String("6"));
    baum.getRightTree().getRightTree().getRightTree().getRightTree().setContent(new String("3"));
    return baum;
  }

  public BinaryTree<String> getBaum2() {
    BinaryTree<String> baum = new BinaryTree<String>(new String("+"));
    baum.getLeftTree().setContent(new String("*"));
    baum.getRightTree().setContent(new String("-"));
    baum.getLeftTree().getLeftTree().setContent(new String("-"));
    baum.getLeftTree().getRightTree().setContent(new String("2"));
    baum.getRightTree().getLeftTree().setContent(new String("+"));
    baum.getRightTree().getRightTree().setContent(new String("7"));
    baum.getLeftTree().getLeftTree().getLeftTree().setContent(new String("3"));
    baum.getLeftTree().getLeftTree().getRightTree().setContent(new String("5"));
    baum.getRightTree().getLeftTree().getLeftTree().setContent(new String("3"));
    baum.getRightTree().getLeftTree().getRightTree().setContent(new String("2"));
    return baum;
  }