小白请教高手问题，今天看了持久化技术的关于一个从文件中读取数据的问题

想要完成一个功能，向EditText里输入数据，数据存放在一个文件夹后，然后按下back键，再重新启动这个程序，再从这个文件里读取数据，出现的是这个数据已经填充在EditText里
下面是代码

MainActivity

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

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.text.TextUtils;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

EditText text;
String content;
FileOutputStream out=null;
BufferedWriter writer=null;
BufferedReader reader=null;
StringBuilder builder;
String str;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
text=(EditText)findViewById(R.id.text);
str=load();
if(!TextUtils.isEmpty(str)){
text.setText(str);
text.setSelection(str.length());
Toast.makeText(getApplicationContext(), "You have succeed!!!",Toast.LENGTH_LONG).show();
}
}
protected void onDestroy() {
super.onDestroy();
content=text.getText().toString();
save(content);
}

public void save(String content) {
    try{
        FileOutputStream out = openFileOutput("data",Context.MODE_PRIVATE);
        writer=new BufferedWriter(new OutputStreamWriter(out));
        writer.write(content);
    }catch(IOException e){
        e.printStackTrace();
    }finally{
        try{
            if(writer!=null){
                writer.close();
            }
        }catch(IOException e){
            e.printStackTrace();
        }

    }
}



public String load(){

try{
    FileInputStream in=openFileInput("data");
    reader=new BufferedReader(new InputStreamReader(in));
    StringBuilder builder= new StringBuilder();
    String line;
    if((line=reader.readLine())!=null){
        builder.append(line);
    }
}catch(IOException e){
    e.printStackTrace();
}finally{
    if(reader!=null){
        try{
            reader.close();
        }catch(final IOException e){
            e.printStackTrace();
        }
    }
}
return builder.toString();

}

}

activity_main
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.IWIN.filepersistencetext.MainActivity" >

<EditText
    android:id="@+id/text"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:hint="type something..." />

http://blog.sina.com.cn/s/blog_90cdca4c01012eo5.html