如何解决字符串输入输出问题？

Question

未打印字符串值。这段代码有什么问题

public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    int a=scan.nextInt();
    double d=scan.nextDouble();
    String s=scan.nextLine();
    System.out.println("String: " + s);
    System.out.println("Double: " + d);
    System.out.println("Int: " + a);
}