What is toString() and why override it?

The toString() method returns a string representation of an object. It's defined in the Object class (the root of all Java classes) and is automatically called when you print an object or concatenate it with a string. Default behavior: class Point { int x, y; } Point p = new Point(); System.out.println(p); // Prints: "Point@1b6d3586" -- useless! // ClassName@hexHashCode -- not meaningful for debugging. Overriding toString(): class Point { int x, y; public Point(int x, int y) { this.x = x; this.y = y; } @Override public String toString() { return "Point(" + x + ", " + y + ")"; } } Point p = new Point(3, 4); System.out.println(p); // "Point(3, 4)" -- meaningful! System.out.println("Location: " + p); // Auto-calls toString() logger.debug("Current position: {}", p); // Also calls toString(). Why override: (1) Debugging — immediately see object state in logs and debugger; (2) Logging — meaningful log messages; (3) Error messages — describe objects in exceptions; (4) Display — show object to users. Best practices for toString(): include the most important fields; don't include sensitive data (passwords, credit card numbers); be concise but informative; use established formats: @Override public String toString() { return "User{id=" + id + ", name='" + name + "', email='" + email + "'}"; }. Libraries: Lombok @ToString, Apache Commons ToStringBuilder, Google Guava Objects.toStringHelper(). @Override annotation ensures you're actually overriding, not creating a new method.