如何从数组中随机选择元素而不重复? [英] How to randomly pick element from array without repeating?

问题描述

我正在开发测验应用程序.我设法用

I am working on an quiz app. I managed to randomized the questions(from an array) with

int position = new Random().nextInt(questions.length);

，但问题不断重复.我要如何在到达10个问题时不再重复重复说明?这是我的代码，如果有帮助的话:

but the questions keep on repeating. How do i make it stop getting when it reaches lets say 10 questions without repeating? Here is my code if it helps:

gcfQuiz.setText(questions[position]);

    gcfButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {

            EditText Answer = (EditText) findViewById(R.id.txtAns1);
            String finAns = Answer.getText().toString();

            if (finAns==answers[position]){

                correct++;
            }
            position++;
            if (position<questions.length)
            {
                gcfQuiz.setText(questions[position]);

            }else {
                Intent in = new Intent(getApplicationContext(), gcfResult.class);
                startActivity(in);
            }
        }
    });

推荐答案

您可以改用 List ，然后删除该元素(如果已选择):

You could use a List instead, and then remove the element if it is chosen:

List<Question> questions = new ArrayList<Question>();
// For Question class, see below.

// Get some random valid index from the list.
int index = new Random().nextInt(questions.size());
// Remove the question from the list and store it into a variable.
Question currQuestion = questions.remove(i);

为您提供信息，我假设 Question 类看起来像这样.通常，此方法比分别具有问题和答案的两个单独的数组要好:

For your information, I assumed the Question class looks like this. This approach is generally better than two separate arrays with questions and answers respectively:

class Question {

    private String text;
    private String answer;

    public Question(String text, String answer) {
        this.text = text;
        this.answer = answer;
    }

    public boolean isCorrectAnswer(String inputAnswer) {
        return Objects.equals(answer, inputAnswer);
    }
}

一些提示

• 我看到您正在使用 == 来比较 String .从不这样做.请改用 equals().请参见如何在Java中比较字符串?.
• 我看到您有一个名为 Answer 的变量.根据Java命名约定，变量应以小写字母开头.请参阅Oracle网站上的代码约定.li>
• 见上文；您可以将检查答案是否正确的责任转移到 Question 类，因为它包含答案字符串.请参见对象必须自行负责

Some tips

• I see you are using == to compare Strings. Never ever do that. Use equals() instead. See How do I compare strings in Java?.
• I see you have a variable named Answer. According to the Java Naming Conventions, variables should start with a lowercase character. See Code Conventions at the Oracle website.
• See above; you could transfer the responsibility of checking whether an answer is correct to the Question class, because it holds the answer string. See An Object Must be Responsible for Itself.

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