Help mediaplayer doesn't play in switch case my program is

[Android Question]

package in.research.hash_table;

import android.media.AudioManager;
import android.media.MediaPlayer;
import android.media.SoundPool;
import android.os.Bundle;

import android.support.v7.app.AppCompatActivity;
import android.widget.TextView;

import java.util.HashMap;
import java.util.Hashtable;
import java.util.Scanner;


public class MainActivity extends AppCompatActivity {

public static Hashtable<String, Integer> LUT=new Hashtable<String, Integer>();;
private MediaPlayer meadiaPlayer=new MediaPlayer();
private static final String str="amio";
Scanner s=new Scanner(str);
TextView tv1,tv2;

int count=0;
SoundPool soundPool;
int soundId;

MediaPlayer mp;

HashMap<String,Integer>ht=new HashMap<String,Integer>();

@override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
soundPool=new SoundPool(1, AudioManager.STREAM_MUSIC,1);
soundId=soundPool.load(this,R.raw.thu,1);
soundPool.play(soundId, 1, 1, 1, 1, 1f);


tv1=(TextView)findViewById(R.id.tv1);
tv2=(TextView)findViewById(R.id.tv2);
tv1.append(str);
for(int i=0;i<str.length();i++){
if(Character.toString(str.charAt(i)).matches("[ameiou]")){
switch(Character.toString(str.charAt(i))){

case "a":
tv2.append("a");
mp=MediaPlayer.create(this,R.raw.a);

break;
case "m":
tv2.append("m");
mp=MediaPlayer.create(this,R.raw.m);

break;
case "i":
tv2.append("i");
mp=MediaPlayer.create(this,R.raw.i);

break;
case "o":
tv2.append("o");
mp=MediaPlayer.create(this,R.raw.o);


break;
case "u":
tv2.append("u");

break;
}





}

mp.start();
count++;



}













}




}