[android] How to find MAC address of an Android device programmatically

It's Working

    package com.keshav.fetchmacaddress;
    
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.util.Log;
    
    import java.net.InetAddress;
    import java.net.NetworkInterface;
    import java.net.SocketException;
    import java.net.UnknownHostException;
    import java.util.Collections;
    import java.util.List;
    
    public class MainActivity extends AppCompatActivity {
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            Log.e("keshav","getMacAddr -> " +getMacAddr());
        }
    
        public static String getMacAddr() {
            try {
                List<NetworkInterface> all = Collections.list(NetworkInterface.getNetworkInterfaces());
                for (NetworkInterface nif : all) {
                    if (!nif.getName().equalsIgnoreCase("wlan0")) continue;
    
                    byte[] macBytes = nif.getHardwareAddress();
                    if (macBytes == null) {
                        return "";
                    }
    
                    StringBuilder res1 = new StringBuilder();
                    for (byte b : macBytes) {
                        // res1.append(Integer.toHexString(b & 0xFF) + ":");
                        res1.append(String.format("%02X:",b)); 
                    }
    
                    if (res1.length() > 0) {
                        res1.deleteCharAt(res1.length() - 1);
                    }
                    return res1.toString();
                }
            } catch (Exception ex) {
                //handle exception
            }
            return "";
        }
    }

UPDATE 1

This answer got a bug where a byte that in hex form got a single digit, will not appear with a "0" before it. The append to res1 has been changed to take care of it.

 StringBuilder res1 = new StringBuilder();
                for (byte b : macBytes) {
                    // res1.append(Integer.toHexString(b & 0xFF) + ":");
                    res1.append(String.format("%02X:",b)); 
                }