java - 如何才能使随机不重复呢？

Question

我创建了一个随机选择显示的字符串列表，因此我想让它不会重复。我怎样才能做到这一点。

public class qustionsActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_qustions);

    final String[] questions = getResources().getStringArray(R.array.coupleQuestions);
    final String randomQuestions = questions[new Random().nextInt(questions.length)];

    final TextView theQuestion = findViewById(R.id.theQustion);

    theQuestion.setText(randomQuestions);

    Button nextQuestion = findViewById(R.id.nextQuestion);

    nextQuestion.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            String randomQuestions = questions[new Random().nextInt(questions.length)];
            theQuestion.setText(randomQuestions);

        }
    });
}

我有两个“randomQuestions”字符串的原因是因为我希望您进入 Activity 后立即显示一个问题，并且单击按钮时它将随机生成一个新字符串。

Answer 1

您可以随机打乱问题并按顺序回答下一个(随机)问题，而不是每次都随机选择。

private final List<String> randomQuestions;
private int questionI;

// Cycling endlessly    
private String nextQuestion() {
    String question = randomQuestions.get(questionI);
    ++questionI;
    if (questionI > randomQuestions.size()) {
        questionI = 0;
    }
}

// Once through the list:    
private String nextQuestion() {
    return randomQuestions.remove(0); // Always take the first, removing it.
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_qustions);

    final String[] questions = getResources().getStringArray(R.array.coupleQuestions);
    randomQuestions = Collections.shuffle(Arrays.asList(questions));