String fileToRead = "path-to-file"; //path to file in the fs
//reads the text file line by line
BufferedReader reader = new BufferedReader(new FileReader(fileToRead));
String curLine = null; //current line string
StringBuilder strBuilder = new StringBuilder(); //using stringbuilder to slowly build the string by appending lines

while ((curLine = reader.readLine()) != null) { //while there are more lines
    strBuilder.append(curLine); //append lines to StringBuilder
}
String input = strBuilder.toString(); //converting strBuilder to string
return input; //and return