JSFiddle - React, Tailwind, and code Playground

HTML

<html>
    <body>
        <code id="java">
            public static void main(String[] args)<br>
            {
            <pre>    int i = 120; </pre><br>
            <pre>    // Displays a message in the console </pre>
            <pre>    // This is a test </pre>
            <pre>    System.out.println( "Hello Big World!" );</pre>
            }<br><br>
            
            public static void main(String[] args)<br>
            {
            <pre>    int i = 120; </pre><br>
            <pre>    // No quotes </pre>
            <pre>    // This is a test </pre>
            }<br><br>
            
            public static void main(String[] args)<br>
            {
            <pre>    int i = 120; </pre><br>
            <pre>    // No quotes </pre>
            <pre>    // This is a 'test', that's all I'll do </pre>
            <pre>    System.out.println( "Hello 'Big' World!" );</pre>
            }
        </code>
    </body>
</html>

CSS

.quotes
{
    font-weight: bold;
    color: #E01B1B;
}

JavaScript

$(document).ready(function() {
    var code  = $("#java").html(); // Get the code
    var split = code.split('\"');  // Split up each element at the "

    // Set the CSS of reserved words, digits, strings, and comments
    for (var j = 0; j < split.length - 1; j++) {
        if (j%2 == 0) { //if first, add beginning
            split[j] = split[j] + '<span class="quotes">"';
        } else {//if second, add ending
            split[j] = split[j] + '"</span>';
        }
    }
    // Join all the split up elements back together!
    $("#java").html(split.join(""));
    
    code  = $("#java").html(); // Get the code
    split = code.split('\'');  // Split up each element at the '
    var openQ = 1;
    var sub1;
    var sub2;

    for (var j = 0; j < split.length - 1; j++) {
        sub1 = split[j+1].substr(0,2); //checking for a contraction of 's
        sub2 = split[j+1].substr(0,3); //checking for a contraction of 'll
        if(sub1 != "s " && sub2 != "ll ") {
          if (openQ) { //if first, add beginning
            split[j] = split[j] + '<span class="quotes">\'';
            openQ = 0;
          } else {//if second, add ending
            split[j] = split[j] + '\'</span>';
            openQ = 1;
          }
        }
        else {//add apostrophe back
            split[j] = split[j] + '\'';
        }
    }
    $("#java").html(split.join(""));
});