How to Read and Write from a File in Android?

package com.example.readwrite_file;
 
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
 
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
 
public class MainActivity extends Activity {
 
    private static final String TAG = MainActivity.class.getName();
    private static final String FILENAME = "myFile.txt";
 
    TextView text;
 
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        text = (TextView) findViewById(R.id.textView1);
 
        Button Read = (Button) findViewById(R.id.read);
        Button write = (Button) findViewById(R.id.writefile);
 
        Read.setOnClickListener(new View.OnClickListener() {
 
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                readFromFile();
                Toast.makeText(getApplicationContext(),
                        "Successfully read From file", Toast.LENGTH_SHORT)
                        .show();
            }
        });
        final String textToSaveString = "Hello Android";
 
        write.setOnClickListener(new View.OnClickListener() {
 
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                writeToFile(textToSaveString);
                Toast.makeText(getApplicationContext(), "Write made to file",
                        Toast.LENGTH_SHORT).show();
 
            }
        });
 
    }
 
    private void writeToFile(String data) {
        try {
 
            FileOutputStream fos = openFileOutput(FILENAME,
                    Context.MODE_PRIVATE);
            fos.write(data.getBytes());
            fos.close();
 
        } catch (IOException e) {
            Log.e(TAG, "File write failed: " + e.toString());
        }
 
    }
 
    private void readFromFile() {
        File file = new File(this.getFilesDir() + "/", FILENAME);
        if (!file.exists()) {
            throw new RuntimeException("File not found");
        }
        Log.e("Testing", "Starting to read");
        BufferedReader reader = null;
        StringBuilder builder = null;
        try {
            reader = new BufferedReader(new FileReader(file));
            builder = new StringBuilder();
            String line;
            while ((line = reader.readLine()) != null) {
                builder.append(line);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        text.setText(builder.toString());
    }
 
}