Java流根据double值对对象进行排序

Question

我有 X1 对象列表，并尝试根据返回 Double 值的方法 obj_function() 对列表进行排序。

result = custom_obj_list.stream()
    .sorted((x1,x2) -> {
        return -x1.obj_function().compareTo(x2.obj_function());
    }).filter((x2) -> { 
        return x2.obj_function <= 1; 
    }).collect(Collectors.toList());

但我正在努力解决以下错误消息

stream().sorted() cannot resolve symbol or cannot resolve method

Answer 1

您可以使用Comparator.comparing而不是 lambda 表达式，如果您只想默认排序顺序

result = custom_obj_list.stream()
                        .sorted(Comparator.comparingDouble(X1::obj_function))  //X1 should be class name
                        .filter(x2 -> x2.obj_function() <= 1)
                        .collect(Collectors.toList());

或反向排序

result = custom_obj_list.stream()
                        .sorted(Comparator.comparingDouble(X1::obj_function).reverse()))   ////X1 should be class name
                        .filter(x2 -> x2.obj_function() <= 1)
                        .collect(Collectors.toList());