how to use AlertDialog in a normal Java class

Question

I want to separate my business logic from the ui and I actually wanted to implement MVVM architecture for that. I have this class that I perform all my business logic but the issue is that the app crashes when it tries to show the AlertDialog that I used in the class because I was using application.getApplicationContext. I cannot be able to access getActivity in a normal class. I really need a way to resolve that because I don't want to move the dialog out of that class. This is the error message that I am getting.

    FATAL EXCEPTION: main
                                                                                                        Process: com.elijahukeme.assessmentapp, PID: 11350
                                                                                                        java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
                                                                                                            at androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor(AppCompatDelegateImpl.java:926)
                                                                                                            at androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor(AppCompatDelegateImpl.java:889)
                                                                                                            at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:772)
                                                                                                            at androidx.appcompat.app.AppCompatDialog.setContentView(AppCompatDialog.java:95)
                                                                                                            at androidx.appcompat.app.AlertController.installContent(AlertController.java:232)
                                                                                                            at androidx.appcompat.app.AlertDialog.onCreate(AlertDialog.java:279)
                                                                                                            at android.app.Dialog.dispatchOnCreate(Dialog.java:407)
                                                                                                            at android.app.Dialog.show(Dialog.java:302)
                                                                                                            at androidx.appcompat.app.AlertDialog$Builder.show(AlertDialog.java:1009)
                                                                                                            at com.elijahukeme.assessmentapp.repositories.AuthenticationRepository.showMessage(AuthenticationRepository.java:205)
                                                                                                            at com.elijahukeme.assessmentapp.repositories.AuthenticationRepository$1.onDataChange(AuthenticationRepository.java:68)
                                                                                                            at com.google.firebase.database.Query$1.onDataChange(Query.java:191)
                                                                                                            at com.google.firebase.database.core.ValueEventRegistration.fireEvent(ValueEventRegistration.java:75)
    
    
    my repository class
    
    public class AuthenticationRepository implements ShowErrorMessage {
        private Application application;
        private MutableLiveData<FirebaseDatabase> mutableLiveData;
        private FirebaseDatabase firebaseDatabase;
        private StorageReference profileImageStorageRef;
        private String myUri ;
    
        public MutableLiveData<FirebaseDatabase> getMutableLiveData() {
            return mutableLiveData;
        }
    
        public FirebaseDatabase getFirebaseDatabase() {
            return firebaseDatabase;
        }
    
        public StorageReference getProfileImageStorageRef() {
            return profileImageStorageRef;
        }
    
        private StudentModel studentModel;
        private RegistrationNumberModel registrationNumberModel;
    
        public AuthenticationRepository(Application application){
            this.application = application;
            mutableLiveData = new MutableLiveData<>();
            firebaseDatabase = FirebaseDatabase.getInstance();
            profileImageStorageRef = FirebaseStorage.getInstance().getReference("Profile Images");
            myUri = "";
        }
    
        public void registerRegistrationNumber(String regNumber, ProgressBar progressBar){
            progressBar.setVisibility(View.VISIBLE);
            firebaseDatabase.getReference().child("Registration Number")
                    .child(regNumber).addListenerForSingleValueEvent(new ValueEventListener() {
                        @Override
                        public void onDataChange(@NonNull DataSnapshot snapshot) {
                            if (snapshot.exists()){
                                progressBar.setVisibility(View.GONE);
                                showMessage("Error","You have already added this Registration Number");
                            }else {
                                HashMap<String,Object> hashMap = new HashMap<>();
                                hashMap.put("regNumber",regNumber);
                                firebaseDatabase.getReference().child("Registration Number")
                                        .child(regNumber).updateChildren(hashMap)
                                        .addOnCompleteListener(new OnCompleteListener<Void>() {
                                            @Override
                                            public void onComplete(@NonNull Task<Void> task) {
                                                if (task.isSuccessful()){
                                                    progressBar.setVisibility(View.GONE);
                                                    Toast.makeText(application, "Registration Number Added Successfully",Toast.LENGTH_SHORT).show();
                                                }else{
                                                    progressBar.setVisibility(View.GONE);
                                                    Toast.makeText(application, "Error Occurred", Toast.LENGTH_SHORT).show();
                                                }
                                            }
                                        });
                            }
                        }
    
                        @Override
                        public void onCancelled(@NonNull DatabaseError error) {
                            progressBar.setVisibility(View.GONE);
                            Toast.makeText(application, error.toString(), Toast.LENGTH_SHORT).show();
                        }
                    });
        }
    
    @Override
        public void showMessage(String title, String message) {
            AlertDialog.Builder builder = new AlertDialog.Builder(application.getApplicationContext());
            builder.setCancelable(true);
            builder.setTitle(title);
            builder.setMessage(message);
            builder.show();
        }
    }
    
    public interface ShowErrorMessage {
        void showMessage(String title, String message);
    }