activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.lnjr.store01.MainActivity" android:orientation="vertical">
    <Button
        android:text="store to File"
        android:onClick="storetoFile"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <Button
        android:text="read From File"
        android:onClick="readFromFile"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        />
    <Button
        android:text="get sd"
        android:onClick="getSd"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <Button
        android:text="store to sharePreferences"
        android:onClick="storeToSp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <Button
        android:text="read from sharePreferences"
        android:onClick="readFromSp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

MainActivity.main

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void storetoFile(View view)throws Exception {
        File file=this.getFileStreamPath("abc.txt");
        OutputStream out=new FileOutputStream(file);
        Log.i("file Path",file.getAbsolutePath());
        out.write(97);
        out.close();
    }
    public void readFromFile(View view) throws Exception{
        File file=this.getFileStreamPath("abc.txt");
        InputStream in=new FileInputStream(file);
        Log.i("this result",in.read()+"");
        in.close();
    }
    public void getSd(View view) {
        File sd= Environment.getExternalStorageDirectory();
        File sdd=Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
        Log.i("sdd card",sdd.getAbsolutePath());
    }
    public void storeToSp(View view) {
        SharedPreferences sharedPreference= PreferenceManager.getDefaultSharedPreferences(this);
        SharedPreferences.Editor editor=sharedPreference.edit();
        editor.putString("User","sll");
        editor.putString("psd","123");
        editor.putInt("age",100);
        editor.commit();
    }
    public void readFromSp(View view) {
    SharedPreferences sharedPreference=PreferenceManager.getDefaultSharedPreferences(this);
    String s=sharedPreference.getString("User","null");
    Log.i("User name",s);
    }
}