if you want creat file and save some data the you want search about data in file use this simple example

MainActivity.java

package com.mostafaanter.file_master;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Toast;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;


public class MainActivity extends Activity {
    private EditText editTextAdd;
    private EditText searchEditText;
    private Button addMessage;
    private Button search;
    private ImageView expression;
    static final int READ_BLOCK_SIZE = 100;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        editTextAdd = (EditText) findViewById(R.id.editText);
        searchEditText = (EditText) findViewById(R.id.editText2);
        addMessage = (Button) findViewById(R.id.button1);
        search = (Button) findViewById(R.id.button2);
        expression = (ImageView) findViewById(R.id.image);



    }
    public void addMessage(View view){
        //---writing to files---
        try {
            FileOutputStream fOut =
                    openFileOutput("textfile.txt", MODE_PRIVATE);
            //---For writing bytes to a fie, use the OutputStreamWriter class and use its write( )  method to write a
            //---string to the fie. To save the changes to the fie, use its close( )  method:
            OutputStreamWriter osw = new OutputStreamWriter(fOut);
            //---write the string to the file---
            osw.write(editTextAdd.getText().toString());
            osw.close();
            //---display file saved message---
            Toast.makeText(getBaseContext(), "File saved successfully! ",
                    Toast.LENGTH_SHORT) .show();
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
    }
    public void searchProcess(View view){
        //---reading from files---
        try
        {
            FileInputStream fIn =
                    openFileInput("textfile.txt");
            InputStreamReader isr = new
                    InputStreamReader(fIn);
            /*---Because you do not know how many characters need to be read from the fie, you use the read( )
            method from the InputStreamReader object to read in the characters in blocks of 100 bytes (you
                can change this to a value reasonable to you). The read( )  method returns the number of characters
            read, and reading continues until there are no more unread characters (it returns -1 when the end of
                the fie is reached):
                ---*/
            char[] inputBuffer = new char[READ_BLOCK_SIZE];
            String s = "";
            int charRead;
            while ((charRead = isr.read(inputBuffer))>0)
            {
                //---convert the chars to a String---
                String readString =
                        String.copyValueOf(inputBuffer, 0,
                                charRead);
                s += readString;
                inputBuffer = new char[READ_BLOCK_SIZE];
            }
            isr.close();
            //-- execute search functionality
            if(s.contains(searchEditText.getText().toString())){
                Toast.makeText(getBaseContext(),
                        "File loaded successfully! " + s,
                        Toast.LENGTH_SHORT) .show();
                expression.setImageResource(R.drawable.smile1);
            }else
                expression.setImageResource(R.drawable.smile2);

        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
    }




}