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copied!<p>A little of spare time produced <strong>a complete example</strong> for your case. Create new RandomMathQuestionGenerator.java file and it is cooked for compilation.</p> <pre><code>import java.util.ArrayList; import java.util.Iterator; import java.util.List; import java.util.Random; public class RandomMathQuestionGenerator { private static final int NUMBER_OF_QUESTIONS = 10; private static final int MIN_QUESTION_ELEMENTS = 2; private static final int MAX_QUESTION_ELEMENTS = 4; private static final int MIN_QUESTION_ELEMENT_VALUE = 1; private static final int MAX_QUESTION_ELEMENT_VALUE = 100; private final Random randomGenerator = new Random(); public static void main(String[] args) { RandomMathQuestionGenerator questionGenerator = new RandomMathQuestionGenerator(); List<Question> randomQuestions = questionGenerator.getGeneratedRandomQuestions(); for (Question question : randomQuestions) { System.out.println(question); } } public List<Question> getGeneratedRandomQuestions() { List<Question> randomQuestions = new ArrayList<Question>(NUMBER_OF_QUESTIONS); for (int i = 0; i < NUMBER_OF_QUESTIONS; i++) { int randomQuestionElementsCapacity = getRandomQuestionElementsCapacity(); Question question = new Question(randomQuestionElementsCapacity); for (int j = 0; j < randomQuestionElementsCapacity; j++) { boolean isLastIteration = j + 1 == randomQuestionElementsCapacity; QuestionElement questionElement = new QuestionElement(); questionElement.setValue(getRandomQuestionElementValue()); questionElement.setOperator(isLastIteration ? null : Operator.values()[randomGenerator.nextInt(Operator.values().length)]); question.addElement(questionElement); } randomQuestions.add(question); } return randomQuestions; } private int getRandomQuestionElementsCapacity() { return getRandomIntegerFromRange(MIN_QUESTION_ELEMENTS, MAX_QUESTION_ELEMENTS); } private int getRandomQuestionElementValue() { return getRandomIntegerFromRange(MIN_QUESTION_ELEMENT_VALUE, MAX_QUESTION_ELEMENT_VALUE); } private int getRandomIntegerFromRange(int min, int max) { return randomGenerator.nextInt(max - min + 1) + min; } } class Question { private List<QuestionElement> questionElements; public Question(int sizeOfQuestionElemets) { questionElements = new ArrayList<QuestionElement>(sizeOfQuestionElemets); } public void addElement(QuestionElement questionElement) { questionElements.add(questionElement); } public List<QuestionElement> getElements() { return questionElements; } public int size() { return questionElements.size(); } @Override public String toString() { StringBuilder sb = new StringBuilder(); for (QuestionElement questionElement : questionElements) { sb.append(questionElement); } return sb.toString().trim(); } } class QuestionElement { private int value; private Operator operator; public int getValue() { return value; } public void setValue(int value) { this.value = value; } public Operator getOperator() { return operator; } public void setOperator(Operator operator) { this.operator = operator; } @Override public String toString() { return value + (operator == null ? "" : " " + operator.getDisplayValue()) + " "; } } enum Operator { PLUS("+"), MINUS("-"), MULTIPLIER("*"), DIVIDER("/"); private String displayValue; private Operator(String displayValue) { this.displayValue = displayValue; } public String getDisplayValue() { return displayValue; } } </code></pre> <p><a href="http://ideone.com/OG39x" rel="nofollow noreferrer">Run and preview.</a> Hope this helps.</p> <p>Thanks to:</p> <ul> <li><a href="https://stackoverflow.com/a/363692/685962">Generating random number in range</a></li> <li><a href="https://stackoverflow.com/a/5034392/685962">Retrieving random element from array</a></li> </ul>

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