You can use:
From android doc:
String MANUFACTURER
The manufacturer of the product/hardware.
String MODEL
The end-user-visible name for the end product.
String DEVICE
The name of the industrial design.
As a example:
String deviceName = android.os.Build.MANUFACTURER + " " + android.os.Build.MODEL;
//to add to textview
TextView textView = (TextView) findViewById(R.id.text_view);
textView.setText(deviceName);
Furthermore, their is lot of attribute in Build class that you can use, like:
os.android.Build.BOARD
os.android.Build.BRAND
os.android.Build.BOOTLOADER
os.android.Build.DISPLAY
os.android.Build.CPU_ABI
os.android.Build.PRODUCT
os.android.Build.HARDWARE
os.android.Build.ID
Also their is other ways you can get device name without using Build
class(through the bluetooth).