Android get telephone IMSI code. Add permission "android.permission.READ_PHONE_STATE"

MainActivity.java

package br.com.luizgadao.pocimsi;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.telephony.TelephonyManager;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView tvImsi = (TextView) findViewById(R.id.tvImsi);
        TelephonyManager telephonyManager = (TelephonyManager) this.getSystemService(TELEPHONY_SERVICE);
        try{
            String imsi = telephonyManager.getSubscriberId();
            if (imsi != null)
                tvImsi.setText("IMSI: " + telephonyManager.getSubscriberId());
        }catch (Exception e){
            e.printStackTrace();
            tvImsi.setText("this device not have GCM-SIM");
        }
    }
}