gistfile1.txt

Pattern tagSafe = Pattern.compile('[a-zA-Z\\s\\d\\-_]');
Matcher tagSafeMatcher = tagSafe.matcher('Pyramid Construction Inc1234_-.');
String[] strArr = new String[]{};
while(tagSafeMatcher.find()){
    system.debug(tagSafeMatcher.group(0));
    strArr.add(tagSafeMatcher.group(0));
}
system.debug(String.join(strArr,''));