BinaryTree/BinaryTree.java

public class BinaryTree {
  private Node rootNode = null;
  
  public BinaryTree() {}

  public BinaryTree(int content) {
    insert(content);
  }

  public boolean search(int value) {
     if (rootNode == null) {
       return false;
     }

     return searchRecursiv(rootNode, value);
  }

  private boolean searchRecursiv(Node node, int value) {
    int content = node.getContent();

    if (value == content) {
      return true;
    } else if (value > content) {
      Node leftNode = node.getLeftNode();
      if (leftNode == null) {
        return false;
      }
      return searchRecursiv(leftNode, value);
    } else if (value < content) {
      Node rightNode = node.getRightNode();
      if (rightNode == null) {
        return false;
      }
      return searchRecursiv(rightNode, value);
    } else {
      System.out.println("Something went wrong!");
      return false;
    }
  }

  public void remove(int value) {
    rootNode = removeRecursiv(rootNode, value);
  }

  private Node removeRecursiv(Node root, int value) {
    if (root == null) {
      return null;
    }
    
    if (value < root.getContent()) {
      root.setLeftNode(removeRecursiv(root.getLeftNode(), value));
    } else if (value > root.getContent()) {
      root.setRightNode(removeRecursiv(root.getRightNode(), value));
    } else {
      if (root.getLeftNode() == null) {
        return root.getRightNode();
      }
      if (root.getRightNode() == null) {
        return root.getLeftNode();
      }
      Node next = findMinimum(root.getRightNode());
      root.setContent(next.getContent());
      root.setRightNode(removeRecursiv(root.getRightNode(), next.getContent())); 
    }
    return root;
  }

  private Node findMinimum(Node root) {
    if (root.getLeftNode() == null) {
      return root;
    }
    return findMinimum(root.getLeftNode());
  }

  public void insert(int content) {
    if (rootNode == null) {
      Node newNode = new Node(content);
      rootNode = newNode;
    } else {
      insertRecursiv(rootNode, content);      
    }
  }

  private void insertRecursiv(Node currentNode, int content) {
    int currentContent = currentNode.getContent();

    // has to be inserted left
    if (currentContent <= content) {
      // if node == null -> insert left
      if (currentNode.getLeftNode() == null) {
        Node newNode = new Node(content);
        currentNode.setLeftNode(newNode);
        System.out.println("Inserted Left");
        return;
      } else {
        // traverse -> 1 down
        insertRecursiv(currentNode.getLeftNode(), content);
        return;
      }
    } else /* insert right */ {
      // if node == null -> insert right
      if (currentNode.getRightNode() == null) {
        Node newNode = new Node(content);
        currentNode.setRightNode(newNode);
        System.out.println("Inserted Right");
        return;
      } else {
        // traverse -> 1 down
        insertRecursiv(currentNode.getRightNode(), content);
        return;
      }
    }
  }



  // Print functions from https://www.baeldung.com/java-print-binary-tree-diagram
  public void print() {
    StringBuilder sb = new StringBuilder();
    traversePreOrder(sb, "", "", rootNode);
    System.out.println(sb.toString());
  }
  
  private void traversePreOrder(StringBuilder sb, String padding, String pointer, Node node) {
    if (node != null) {
        sb.append(padding);
        sb.append(pointer);
        sb.append(node.getContent());
        sb.append("\n");

        StringBuilder paddingBuilder = new StringBuilder(padding);
        paddingBuilder.append("|  ");

        String paddingForBoth = paddingBuilder.toString();
        String pointerForRight = "---";
        String pointerForLeft = (node.getRightNode() != null) ? "+--" : "'--";

        traversePreOrder(sb, paddingForBoth, pointerForLeft, node.getLeftNode());
        traversePreOrder(sb, paddingForBoth, pointerForRight, node.getRightNode());
    }
  }
}