How to validate EditText input with a custom regex in Android?

I am new to android development and also regular expression. I am able to retrieve inputs from user through the EditText and check if it's empty and later display the error message if it is empty but I am not sure on how to check with a custom regex. Here's my code :

 myInput = (EditText) findViewById(R.id.myInput);
String myInput_Input_a = String.valueOf(myInput.getText());

//replace if input contains whiteSpace
String myInput_Input = myInput_Input_a.replace(" ","");


    if (myInput_Input.length()==0 || myInput_Input== null ){

               myInput.setError("Something is Missing! ");
     }else{//Input into databsae}

So, im expecting the user to input a 5 character long string where the first 2 letters must be numbers and the last 3 characters must be characters. So how can i implement it people ?