小编joe*_*ens的帖子

有一种方法get(sql)(我不能修改它).这个方法返回MyObjects,它必须在try catch块中,因为JqlParseException那里是可能的.我的代码是:

String sql = something;
try{
   MyObject object = get(sql);
} catch(JqlParseException e){
   e.printStackTrace();
} catch(RuntimeException e){
   e.printStackTrace();
}

我想删除try catch并使用Optional类,我试过:

MyObject object = Optional.ofNullable(get(sql)).orElseThrow(RuntimeException::new);

但是那里的IDE力量也尝试了.并为:

MyObject object = Optional.ofNullable(get(sql)).orElseThrow(JqlParseException::new));

是一个错误(在IDE中)The type JqlParseException does not define JqlParseException() that is applicable.有没有办法避免尝试catch块并使用可选的？

我有一个简单的类,有三个值:

class Book{
   private String title;
   private String author;
   private double price;
}

title是独一无二的(永远).有一个选定的标题列表(as List<String>)和每个Book系统的列表.我希望Book从标题列表中获取所有密钥.我的代码是:

List<Book> allBooks = getAllBooks();
List<String> selectedTitles = getSelectedTitles();
List<Book> selectedBooks = allBooks.stream().
   filter(x -> selectedTitles.contains(x.getTitle())).
   collect(Collectors.toList());

它的工作原理,但是选择的allBook书籍是通过insted 来订购的selectedTitles.例如:

allBooks(only title) = {"A","B","C","D"}
selectedTitles = {"B","A","D"}
selectedBooks(only title) = {"A","B","D"}

怎么可能(通过stream()订购selectedTitles？)(这个例子应该是{"B","D","A"}？