android studio如何设置一些TextViews id

<TextView
    android:id="@+id/myTextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello World!" />

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

public class MainActivity extends AppCompatActivity {
    private TextView myTextView;

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

        // 通过id获取TextView控件
        myTextView = findViewById(R.id.myTextView);

        // 对TextView进行操作
        myTextView.setText("Hello Android!");
    }
}