How to fix "Underfull \hbox (badness 10000)" warning?

I have this small .tex file.

\documentclass{article}
\usepackage[T2A]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{titling}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{tikz}
\setlength{\droptitle}{-3.5cm}
\setlength{\parindent}{0cm}
\newcommand{\squad}{\hspace{0.5em}}
\author{vladgovor77771}
\title{Some article}
\begin{document}
\maketitle
\textbf{Task 1} \newline
Task description: \newline
\end{document}

When compiling, it warns about line

\textbf{Task 1} \newline

With the following message:

"Underfull \hbox (badness 10000)".

How do I fix this?

3 Answers

I had a similar issue, I solved it by removing any \newline or \\ at the and of every sentence that had nothing textual below.

For instance, two examples that causes that problem:

An example. \\
This is well used. \\
This line will cause the error. \\
(I'm a new paragraph) \\
Because there's nothing directly underneath.\\
The last line does NOT require a "newline".
This is a thid paragraph. \\
:D

The same is true for figures or similar

This is a line.
Putting a "newline", as here, before a \begin will cause the error. \\
\begin{figure}[h]
....
\end{figure}

Instead of forcing an underfull box with \newline, you could simply leave an empty line to start a new paragraph:

\documentclass{article}
\usepackage[T2A]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{titling}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{tikz}
\setlength{\droptitle}{-3.5cm}
\setlength{\parindent}{0cm}
\newcommand{\squad}{\hspace{0.5em}}
\author{vladgovor77771}
\title{Some article}
\begin{document}
\maketitle
\textbf{Task 1}
Task description:
blabla
\end{document}

A quick and nice solution is to use package parskip, and instead of using \newline or \\ for line breaks, simply insert an empty line

\documentclass{article}
\usepackage[T2A]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{titling}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{tikz}
\usepackage{parskip} %% <-- added
\setlength{\droptitle}{-3.5cm}
\setlength{\parindent}{0cm}
\newcommand{\squad}{\hspace{0.5em}}
\author{vladgovor77771}
\title{Some article}
\begin{document}
\maketitle
\textbf{Task 1}
Task description:
\end{document}

The warning will be gone.

By the way, to know why it happened, refer to this question on TeX Stack Exchange.