nfc 아이디 값에 따라 액티비티 전환하는 방법 알고 싶습니다 ㅠ

Question

package com.example.opwer.myfinal;

import android.app.Activity;
import android.app.PendingIntent;
import android.content.Intent;
import android.nfc.NfcAdapter;
import android.nfc.Tag;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class tagActivity extends Activity {

    private NfcAdapter nfcAdapter;
    private PendingIntent pendingIntent;

    private TextView tagDesc;
    public String str;

    private String id1 = "04563E52274980";
    private String id2 = "04463E52274980";
    private String id3 = "04423E52274980";

    private Intent intent;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_tag);

        tagDesc = (TextView)findViewById(R.id.tagDesc);

        nfcAdapter = NfcAdapter.getDefaultAdapter(this);


//        Intent intent = new Intent(this, ImgActivity.class);

        intent = new Intent(this, ImgActivity.class).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
        pendingIntent = PendingIntent.getActivity(this, 0, intent, 0);

        if(str == id1 || str == id2 || str == id3){

            startActivity(intent);

        }

    }

    @Override
    protected void onPause() {
        if (nfcAdapter != null) {
            nfcAdapter.disableForegroundDispatch(this);
        }
        super.onPause();
    }

    @Override
    protected void onResume() {
        super.onResume();
        if (nfcAdapter != null) {
            nfcAdapter.enableForegroundDispatch(this, pendingIntent, null, null);
        }
    }

    @Override
    protected void onNewIntent(Intent intent) {
        //super.onNewIntent(intent);

        Tag tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
       if (tag != null) {
            byte[] tagId = tag.getId();
            str = toHexString(tagId);
            tagDesc.setText("TagID: " + str);

       }

    }


    public static final String CHARS = "0123456789ABCDEF";

    public  String toHexString(byte[] data) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < data.length; ++i) {
            sb.append(CHARS.charAt((data[i] >> 4) & 0x0F))
                    .append(CHARS.charAt(data[i] & 0x0F));
        }
        return sb.toString();

    }
}

이런식으로 짰는데 ... 액티비티 전환이 되긴 하는데 아이디값을 판별못하는것같아요 .. 다른 아이디값의 NFC를 태깅해도 넘어가더라구요.. 

어떻게 하면 아이디값에 따라 다른 액티비티를 전환할 수 있을까요?