How to restart activity after chaining it theme?

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Android

Hell I have create an app to change the theme between Day and Night it work fine but the problem is to how to apply the theme immediately after the button clike I'm using sharedpreference to save whether it was night or day.
This is main activity:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    SharedPreferences sharepref= 
PreferenceManager.getDefaultSharedPreferences(this);
    Boolean swichter =sharepref.getBoolean(this.KEY_PREF_STRING,true);
    Toast.makeText(this,swichter.toString(),Toast.LENGTH_LONG).show();
    if (swichter.toString()=="false"){
        AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
        Intent intent=getIntent();
        finish();
        startActivity(intent);
    }else{
        AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
        Intent intent=getIntent();
        finish();
        startActivity(intent);
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    if (id == R.id.action_settings) {
        // launch settings activity
        startActivity(new Intent(MainActivity.this, SettingsActivity.class));
        return true;
    }

Setting Activiry :

public static final String KEY_PREF_STRING="key_vibrate";

getSupportFragmentManager().beginTransaction()
            .replace(android.R.id.content,new SettingsFragment())
            .commit();

What I have tried:

I have used this.recreate(); and Intent intent=getIntent startAcivity method!