java.lang.RuntimeException: Unable to start activity ComponentInfo: java.lang.ClassCastException: cannot be cast to android.widget.Button

I tried to get this code working using android studio but the app in the emulator crashes everytime I run it and displays an error which is "App has stopped". I looked at the logcat and got this error.

Logcat:

02-11 12:39:49.826 4852-4852/co5025.example.com.week10 E/AndroidRuntime: FATAL EXCEPTION: main
Process: co5025.example.com.week10, PID: 4852
java.lang.RuntimeException: Unable to start activity ComponentInfo{co5025.example.com.week10/co5025.example.com.week10.MainActivity}: java.lang.ClassCastException: android.support.v7.widget.AppCompatEditText cannot be cast to android.widget.Button
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
Caused by: java.lang.ClassCastException: android.support.v7.widget.AppCompatEditText cannot be cast to android.widget.Button
at co5025.example.com.week10.MainActivity.onCreate(MainActivity.java:42)
at android.app.Activity.performCreate(Activity.java:6664)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2599)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707) 
at android.app.ActivityThread.-wrap12(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:154) 
at android.app.ActivityThread.main(ActivityThread.java:6077) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755) 

MainActivity.java

package co5025.example.com.week10;

            import android.app.FragmentManager;
            import android.content.Intent;
            import android.os.Bundle;
            import android.support.design.widget.FloatingActionButton;
            import android.support.design.widget.Snackbar;
            import android.support.v7.app.AppCompatActivity;
            import android.support.v7.widget.Toolbar;
            import android.view.Menu;
            import android.view.MenuItem;
            import android.view.View;
            import android.widget.Button;
            import android.widget.EditText;
            import android.widget.TextView;
            import android.support.v4.app.FragmentManager.BackStackEntry;

            public class MainActivity extends AppCompatActivity implements View.OnClickListener {
                EditText editUsername;
                EditText editPassword;
                TextView errorMessage;
                Button butLogin;
                private FragmentManager.BackStackEntry v;

                @Override
                protected void onCreate(Bundle savedInstanceState) {
                    super.onCreate(savedInstanceState);
                    setContentView(R.layout.activity_main);
                    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
                    setSupportActionBar(toolbar);

                    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
                    fab.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View view) {
                            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                                    .setAction("Action", null).show();
                        }
                    });
                    editPassword    =   (EditText)  findViewById(R.id.edit_password);
                    editUsername    =   (EditText)  findViewById(R.id.edit_username);
                    butLogin    =   (Button) findViewById(R.id.edit_username);
                    butLogin.setOnClickListener(this);

                    if (getIntent().getBooleanExtra("EXIT", false)) finish();
                }

                @Override
                public void onClick(View view) {
                    if  (checkPassword())   {
                        Intent  i;
                        switch  (v.getId()) {
                            case    R.id.but_login:
                                i   =   new Intent(this,    GameActivity.class);
                                startActivity(i);
                                break;
                        }
                    }else{
                        errorMessage    =   (TextView)  findViewById(R.id.error_message);
                        errorMessage.setText("Error: Incorrect Password/Username. Try again!");
                    }
                }

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    // Inflate the menu; this adds items to the action bar if it is present.
                    getMenuInflater().inflate(R.menu.menu_main, menu);
                    return true;
                }

                @Override
                public boolean onOptionsItemSelected(MenuItem item) {
                    // Handle action bar item clicks here. The action bar will
                    // automatically handle clicks on the Home/Up button, so long
                    // as you specify a parent activity in AndroidManifest.xml.
                    int id = item.getItemId();

                    //noinspection SimplifiableIfStatement
                    if (id == R.id.action_settings) {
                        return true;
                    }

                    return super.onOptionsItemSelected(item);
                }

                public  boolean checkPassword(){
                    if  (editUsername.getText().toString().equals("test")   &&
                            (editPassword.getText().toString().equals("1234")))
                        return  true;
                    else
                        return  false;
                }
            }