TheAlgorithms/Java · error · RuntimeException

The element to be deleted does not exist!

Error message

The element to be deleted does not exist!

What it means

Thrown by DoublyLinkedList.delete(int x) when the value x is not found in any node. The method walks from head to tail comparing values; reaching tail without a match triggers RuntimeException. Unlike an IndexOutOfBounds, this is a value-not-found condition.

Source

Thrown at src/main/java/com/thealgorithms/datastructures/lists/DoublyLinkedList.java:305

        }
        --size;
        return temp;
    }

    /**
     * Delete the element from somewhere in the list
     *
     * @param x element to be deleted
     * @return Link deleted
     */
    public void delete(int x) {
        Link current = head;

        while (current.value != x) { // Find the position to delete
            if (current != tail) {
                current = current.next;
            } else { // If we reach the tail and the element is still not found
                throw new RuntimeException("The element to be deleted does not exist!");
            }
        }

        if (current == head) {
            deleteHead();
        } else if (current == tail) {
            deleteTail();
        } else { // Before: 1 <--> 2(current) <--> 3
            current.previous.next = current.next; // 1 --> 3
            current.next.previous = current.previous; // 1 <--> 3
        }
        --size;
    }

    /**
     * Inserts element and reorders
     *
     * @param x Element to be added

View on GitHub (pinned to fdfb9a395b)

Solutions

1. Check membership with a contains/search before delete.
2. Catch RuntimeException (or a custom subclass) and treat not-found as a no-op.
3. Make delete idempotent by wrapping it: try { delete(x); } catch (RuntimeException ignored) {}.
4. Avoid double-processing the same value across threads with a coordinating lock or set.

Example fix

// before
dll.delete(x); // throws if x absent

// after
try {
    dll.delete(x);
} catch (RuntimeException e) {
    // element already absent — safe to ignore
}

try {
    dll.delete(x);
} catch (RuntimeException e) {
    // element not present — treat as no-op
}

When it happens

Trigger: Deleting a value never inserted. Deleting after the element was already removed. Type mismatch where int comparison silently fails (e.g., expecting a value from a different domain).

Common situations: Idempotent cleanup code that retries deletes. Concurrent deletes where one thread removes the value before another. Integer value confusion (signed/unsigned, encoding).

Related errors

• Cannot add null element to the list
• Position out of bounds
• Cannot add null element to the list
• Position out of bounds
• Element cannot be null

AI-assisted analysis of TheAlgorithms/Java@fdfb9a395b (2026-08-13). Data as JSON: /api/errors/6466d6d137f08f43. Report an issue: GitHub.