How to use full width table in LaTeX?

I would write column headers in two lines. In such a case, your table can be fit in one column:

In above table I use tabularx for table environment, booktabs for rules in table and siunitx for columns with numbers (which are now aligned at decimal points).

\documentclass[12pt,journal,compsoc]{IEEEtran}
\usepackage{booktabs,
            tabularx}
\newcommand\mcbf[1]{\multicolumn{1}{>{\centering\arraybackslash\bfseries}X}{#1}}
\usepackage{siunitx}
\usepackage{etoolbox}
\newrobustcmd{\B}{\fontseries{b}\selectfont} % non-extended bold font

\usepackage{lipsum}

\begin{document}
\lipsum[1]
    \begin{table}[htb]
\sisetup{table-format=1.3,
         detect-weight}

    \begin{tabularx}{\linewidth}{@{} l *{4}{S} @{}}
    \toprule
 \multicolumn{5}{c}{F1-accuracy} \\
    \midrule
\mcbf{Methods}
            &   \mcbf{first dataset}
                        &   \mcbf{second dataset}
                                    &   \mcbf{third dataset}
                                                &   \mcbf{forth dataset}\\
    \midrule
 first      & 0.878     & 0.648     & 0.858     & 0.486     \\
 second     & 0.879     & 0.654     & 0.857     & 0.480     \\
third       & 0.863     & 0.664     & 0.855     & {--}      \\
forth       & 0.855     & 0.664     & 0.856     & {--}      \\
fifth       & 0.858     & 0.691     & 0.868     & 0.528     \\
    \midrule
\textbf{sixth}
            & \B 0.89   & \B 0.686  & \B 0.873  & \B 0.565  \\
    \bottomrule
\end{tabularx}
    \end{table}\lipsum[2]
    \begin{figure}[htb]
\includegraphics[width=\linewidth]{final.png}
\caption{F1-accuracy of reuters and slashdot dataset}
\label{fig:FeatLearn}
    \end{figure}
 \lipsum[3]
    \begin{figure}[htb]
\includegraphics[width=\linewidth]{final_rc3.png}
\caption{F1-accuracy of rcv1 and aapd dataset}
\label{fig:FeatLearn}
    \end{figure}
\lipsum[4]

\end{document}

Edit: With above table you will not have problems with overlapping images over table (with compiling above MWE (minimal Working Example) you can confirm thhis). Also table now has more professional look.