JAVA throws exception

Question

public class Test {
public static void main(String[] args) {
Book bookA = new Book("JAVA",79.8);
Book bookB = (Book) bookA.clone();
}
}

请问我在输出克隆对象时，向下转型时红色的字条报错了，说要加上throws ecception是为什么呢？刚学java不久小白一枚，希望各位老哥帮忙解答一下