是否有一种类型安全的方法将空列表作为参数传递给java？

Question

The following code gives a compile error:

public void method(List<String> aList) {}

public void passEmptyList() {
    method(Collections.emptyList());
}

Is there a way to pass an empty list to method without

• Using an intermediate variable
• Casting
• Creating another list object such as new ArrayList<String>()

?

Answer 1

Replace

method(Collections.emptyList());

with

method(Collections.<String>emptyList());

The <String> after the . is an explicit binding for emptyList 's type parameter, so it will return a List<String> instead of a List<Object> .

Answer 2

You can specify the type param like so:

public void passEmptyList() {
    method(Collections.<String>emptyList());
}