Quando tento organizar as activitys para chamar o formulario de cadastro de alunos é gerado o erro de : Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.material.floatingactionbutton.FloatingActionButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

package agrotis.one.ui.activity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import com.google.android.material.floatingactionbutton.FloatingActionButton;


import agrotis.one.DAO.AlunoDAO;
import agrotis.one.R;

import static agrotis.one.R.id.activity_lista_alunos_fab_novo_aluno;

public class ListaAlunosActivity extends AppCompatActivity {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setTitle("Lista de Alunos");

        FloatingActionButton botaoNovoAluno = findViewById(activity_lista_alunos_fab_novo_aluno);
        botaoNovoAluno.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startActivity(new Intent(ListaAlunosActivity.this,
                        CadastroAlunoActivity.class
                ));
            }
        });
        setContentView(R.layout.activity_lista_alunos);

        AlunoDAO dao = new AlunoDAO();

        ListView listaDeAlunos= findViewById(R.id.activity_lista_alunos_list_view);
        listaDeAlunos.setAdapter(new ArrayAdapter<>(this, android.R.layout.simple_list_item_1,dao.todos()));
    }
}