/**
 * 数学题目类
 * 存储题目表达式和答案
 */
public class MathQuestion {
    private String expression;
    private String answer;
    
    public MathQuestion(String expression, String answer) {
        this.expression = expression;
        this.answer = answer;
    }
    
    public String getExpression() {
        return expression;
    }
    
    public String getAnswer() {
        return answer;
    }
    
    @Override
    public String toString() {
        return expression;
    }
    
    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        MathQuestion that = (MathQuestion) obj;
        return expression.equals(that.expression);
    }
    
    @Override
    public int hashCode() {
        return expression.hashCode();
    }
}