Q:

Android Studio Class or interface expected

The problem as seen in the title appears in line 102 of the code down below.  Im very new to this topic and Im trying to make an app which can control an arduino... This part of code I show you is supposed to manage the connection to the Bluetooth Module and in my MainActivity I plan to send the letters to the other device. 
I hope someone can help. 
My code (BT_Classic.java):
    package com.car.bluetooth.bluetoothcar;

import androidx.appcompat.app. AppCompatActivity;

import android.app. ProgressDialog;
import android.bluetooth. BluetoothAdapter;
import android.bluetooth. BluetoothDevice;
import android.bluetooth. BluetoothSocket;
import android.content. Intent;
import android.os. Bundle;
import android.view. View;
import android.widget. AdapterView;
import android.widget. ArrayAdapter;
import android.widget. Button;
import android.widget. ListView;

import java.io. IOException;
import java.util. ArrayList;
import java.util. Set;
import java.util. UUID;

public class BT_Classic extends AppCompatActivity {

private Button pairedButton;
private Button discoveredButton;
private Button btonButton;
private Button btoffButton;
private ProgressDialog progress;
ListView listView;
BluetoothSocket bluetoothSocket;
BluetoothDevice bluetoothDevice;

private final static UUID uuid = UUID.fromString("fc5ffc49-00e3-4c8b-9cf1-6b72aad1001a");

private ArrayList<String> mDeviceList = new ArrayList<String>();

BluetoothAdapter btAdapter = BluetoothAdapter.getDefaultAdapter();

//BLUETOOTH VERBINDUNG

private static final int REQUEST_ENABLED = 0;
private static final int REQUEST_DISCOVERABLE = 0;

    private class ConnectingThread extends Thread {

        public ConnectingThread(BluetoothDevice device) {

            BluetoothSocket temp = null;
            BluetoothDevice bluetoothDevice = device;

            // Get a BluetoothSocket to connect with the given BluetoothDevice
            try {
                temp = bluetoothDevice.createRfcommSocketToServiceRecord(uuid);
            } catch (IOException e) {
                e.printStackTrace();
            }
            bluetoothSocket = temp;

        }

            public void run() {
        // Cancel any discovery as it will slow down the connection
        btAdapter.cancelDiscovery();

        try {
            // This will block until it succeeds in connecting to the device
            // through the bluetoothSocket or throws an exception
            bluetoothSocket.connect();
        } catch (IOException connectException) {
            connectException.printStackTrace();
            try {
                bluetoothSocket.close();
            } catch (IOException closeException) {
                closeException.printStackTrace();
            }
        }

        // Code to manage the connection in a separate thread
    /*
        manageBluetoothConnection(bluetoothSocket);
    */
    }

    // Cancel an open connection and terminate the thread
    public void cancel() {
        try {
            bluetoothSocket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

}

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

    pairedButton = (Button) findViewById(R.id.pairedButton);
    discoveredButton = (Button) findViewById(R.id.discoveredButton);
    btonButton = (Button) findViewById(R.id.btonButton);
    btoffButton = (Button) findViewById(R.id.btoffButton);

    listView.setOnItemClickListener(new AdapterView. OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<? > parent, View view, int position, long id) {
            String  itemValue = (String) listView.getItemAtPosition(position);
            String MAC = itemValue.substring(itemValue.length() - 17);
            BluetoothDevice bluetoothDevice = btAdapter.getRemoteDevice(MAC);
            // Initiate a connection request in a separate thread
            ConnectingThread t = new ConnectingThread(bluetoothDevice);
            t.start();
        }
    });

    //Pairing Button

    pairedButton.setOnClickListener(new View. OnClickListener() {
        @Override
        public void onClick(View v) {
            Set<BluetoothDevice> pairedDevices = btAdapter.getBondedDevices();

            ArrayList<String> devices = new ArrayList<String>();

            for (BluetoothDevice bt : pairedDevices){
                devices.add(bt.getName());
                devices.add(bt.getAddress());

            }

            ArrayAdapter arrayAdapter = new ArrayAdapter(BT_Classic.this, android. R.layout.simple_list_item_1, devices);
            listView.setAdapter(arrayAdapter);
        }
    });

    discoveredButton.setOnClickListener(new View. OnClickListener() {
        @Override
        public void onClick(View v) {

            if(!btAdapter.isDiscovering()){
                Intent bton = new Intent(BluetoothAdapter. ACTION_REQUEST_DISCOVERABLE);
                startActivityForResult(bton, REQUEST_DISCOVERABLE);
            }

        }
    });

    btonButton.setOnClickListener(new View. OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent bton = new Intent(BluetoothAdapter. ACTION_REQUEST_ENABLE);
            startActivityForResult(bton, REQUEST_ENABLED);
        }
    });

    btoffButton.setOnClickListener(new View. OnClickListener() {
        @Override
        public void onClick(View v) {
            btAdapter.disable();
        }
    });

}
}

A:

You have an extra } in this section
public void cancel() {
        try {
            bluetoothSocket.close();
        } catch (IOException e) {
            e.printStackTrace();
        } // Close try
    } // Close cancel()
} // Close ConnectingThread

} // DELETE THIS CURLY BRACE

