我有一个应用程序,用户向我提供字段名称,例如name
or costInCents
,我必须按该字段排序。我有办法保证字段名称是正确的。这个应用程序导致了我根本无法上课的复杂情况Comparable
并实施具体的compareTo()
,因为自定义实现compareTo()
我需要知道在实现时使用哪些字段/方法。
因此,为了实现这个目标,我尝试使用反射来将字段与其访问器相匹配。这是我想做的 MWE。
Class Product
是一个简单的 POJO 类,我想对其实例进行成对比较:
public class Product
{
final String name;
final Integer quantity;
final Long costInCents;
public Product(final String name, final Integer quantity, final Long costInCents)
{
this.name = name;
this.quantity = quantity;
this.costInCents = costInCents;
}
public String getName()
{
return name;
}
public Integer getQuantity()
{
return quantity;
}
public Long getCostInCents()
{
return costInCents;
}
}
And my Main
类,目前不完整:
public class Main {
public static void main(String[] args) {
final Product[] productArray =
{
new Product("Clorox wipes", 50, 700L),
new Product("Desk chair", 10, 12000L),
new Product("TV", 5, 30000L),
new Product("Bookcase", 5, 12000L),
new Product("Water bottle", 20, 700L),
};
// The following void methods are supposed to sort in-place with something like Arrays.sort() or Collections.sort(),
// but I am also open to solutions involving stuff like Stream::sorted() or similar ones, which return a sorted array.
sortByField(productArray, "costInCents");
sortByField(productArray, "name");
}
private void sortByField(final Product[] productArray, final String sorterFieldName)
{
final Field sorterField = getSorterField(sorterFieldName, LiteProduct.class); // Gets the Field somehow
final Method sorterAccessor = getSorterAccessor(sorterField, LiteProduct.class); // Given the Field, this is easy
Arrays.sort((Product p1, Product p2)->((Comparable<?>)sorterAccessor.invoke(p1)).compareTo(sorterAccessor.invoke(p2)) > 0); // Capture of ? instead of Object
}
}
不幸的是,Arrays.sort()
行会导致编译时错误并显示消息Capture of ? instead of Object
。我尝试将第二个参数转换为Comparable<?>
, Comparable<? super sorterField.getType()
等等,但没有运气。有想法吗?