Why is my String names accepting integers instead of letters?

You have to use next() in reading the name instead of nextLine() . And also in option 2 you have to use the variable i instead of indice in System.out.println of the student. The code is incomplete for what I checked, but this piece would look like this:

public class Tp1 {

  public static void main(String[] args) {

    final int qtdAlunos = 5;
    String[] nomes = new String[qtdAlunos];
    double[] av1 = new double[qtdAlunos];
    double[] av2 = new double[qtdAlunos];

    int indiceAluno = 0;

    boolean continuar = true;

    do {

      Scanner s = new Scanner(System.in);
      System.out.println("---Bem Vindo---");
      System.out.println("1. Cadastrar Alunos");
      System.out.println("2. Buscar Aluno");
      System.out.println("3. Consultar Notas");
      System.out.println("4. Sair");

      String opcao = s.nextLine();

      switch (opcao) {

        case "1":
          if (indiceAluno < qtdAlunos) {

            System.out.println("Opcao 1 escolhida.");
            Scanner t = new Scanner(System.in);

            System.out.println("Digite o codigo do aluno.");
            int codigo = t.nextInt();
            System.out.println("Digite o nome do Aluno.");
            nomes[indiceAluno] = t.next();
            System.out.println("Digite a nota av1:");
            av1[indiceAluno] = t.nextDouble();
            System.out.println("Digite a nota av2:");
            av2[indiceAluno] = t.nextDouble();

            System.out.println(" nota do aluno" + indiceAluno);
            indiceAluno = indiceAluno + 1;
          }
          break;

        case "2":

          Scanner s2 = new Scanner(System.in);
          int indice = s2.nextInt();
          for (int i = 0; i < nomes.length; i++) {
            if (indiceAluno < qtdAlunos) {
              System.out.println("Nome do aluno: " + nomes[i]);
              System.out.println("Nota do Av1: " + av1[i]);
              System.out.println("Nota do Av2: " + av2[i]);

            } else {
              System.out.println("");
            }
          }
      }

    } while (true);
  }
}