How to make an array that increases if the user wishes?

I have a problem in a programming project. The program asks for the following:

• This is a Question Database (for example, an ENEM, or Vestibular).

• I need to do some commands like add students, teachers, tell who you are, and if you do not 'add' it, but that part is already done. I made ArrayList, for both (any suggestions? I'm open to anything!)

• I need to add questions if you are a teacher. I made a teacher variable, which is boolean , and can "register" in the program as one, or with a student. However, how do I array increase in size when the teacher adds new questions? I've done array of two dimensions, because I need to add questions for each year (Philosophy [QUESTION] [YEAR], Philosophy [3] [0], Philosophy [3] [1], Philosophy [3] [2] , different issues, from different years!) . Also, as far as the answers to each question are concerned, I made another array that has the same size as the questions, which corresponds to it, for example, an array of Sociology, with X questions for the 3 years, I I made another, of answers, with the X questions, with each answer separated each with a '|', for each year.

Any suggestions? package final

package projetofinal;

public class provaQuestoes {
    String[][] Biology = new String[0][3];
    String[][] BiologyAnswer = new String[0][3];
    //Claro que, para cada matéria, mas esse é só um exemplo

    String questionBiology(int year, int question){
        return Biology [year][question];
    }//Cada matéria tem um método que faz isso

    void chooseSubject(int y, int subject, int question){
        switch(subject){
            case 1:
                questionBiology(question, y);
                break;
               // Cada matéria tem um valor que corresponde a um método que envia uma pergunta,
               // porquê eu preciso também que eu crie um teste para o aluno,
               // mas isso é para depois

    [..]
    void addQuestion(int subject, String question, String answers,int y){
        switch(subject){
            case 1:
        \insira o código aqui
            break;

This is a class that has all the subjects of each year. The main is another class, where I made a "decorated" menu, all in text, with a case, which allows user registration (student / teacher), entry as one of these two, with name registration, question record and other things.