import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        String name = "unfichier.txt";
        ecrireFichier(name);
        lireFichier(name);
    }

    public void ecrireFichier(String name)
    {
        String contenu = "Une premiere ligne\nUne seconde ligne";

        FileOutputStream fileOutputStream = null;
        try {
            fileOutputStream = openFileOutput(name, Context.MODE_PRIVATE);
            fileOutputStream.write(contenu.getBytes());
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fileOutputStream != null)
                try {
                    fileOutputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
        }
    }

    public void lireFichier(String name)
    {
        FileInputStream fileInputStream = null;
        StringBuilder stringBuilder = null;

        try {
            fileInputStream = openFileInput(name);
            InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);

            stringBuilder = new StringBuilder();
            String line;

            while((line = bufferedReader.readLine()) != null){
                stringBuilder.append(line + "\n");
            }

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fileInputStream != null)
                try {
                    fileInputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
        }

        if (stringBuilder != null)
            System.out.println(stringBuilder);
        else
            System.err.println("stringBuilder est null");
    }
}