[Q] [Q} Coding a system seting toggle - Android Q&A, Help & Troubleshooting

I am trying to make an app that on launch reads the current on/off(1,0) value of /sys/class/mdnie/mdnie/negative, then changes it to "0 or 1. Someone suggested the below, and I tried it and it does nothing any help is apreciated. Obvously I am a beginner and barely know how to write code but hey gotta start somewhere, this is for a visually impaired friend to toggle negative color mode by assigning a shortcut key to the app. I think it has to do with needing root permision to edit those settings.
Code:
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
import android.app.Activity;
import android.os.Bundle;
public class ToggleNegativeColorsActivity extends Activity {
private static final String FILEPATH = "/sys/class/mdnie/mdnie/negative";
@Override
public void onCreate(Bundle savedInstanceState) {
try {
String value = readFileAsString(FILEPATH);
if ("1".equals(value.trim())) {
writeStringToFile(FILEPATH, "0");
}
else {
writeStringToFile(FILEPATH, "1");
}}
catch (IOException e) {
e.printStackTrace();
}
finish();
}
// Grabbed from http://stackoverflow.com/questions/1656797/how-to-read-a-file-into-string-in-java
private String readFileAsString(String filePath) throws IOException {
StringBuffer fileData = new StringBuffer();
BufferedReader reader = new BufferedReader(
new FileReader(filePath));
char[] buf = new char[1024];
int numRead;
while((numRead=reader.read(buf)) != -1){
String readData = String.valueOf(buf, 0, numRead);
fileData.append(readData);
}
reader.close();
return fileData.toString();
}
// Grabbed from http://stackoverflow.com/questions/1053467/how-do-i-save-a-string-to-a-text-file-using-java
private void writeStringToFile(String filePath, String value) throws IOException {
PrintWriter out = new PrintWriter(filePath);
out.print(value);
out.close();
}
}