Java toArray(new String[0]); 中 new String[0] 有什么用？
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What's the use of new String[0] in toArray(new String[0]);
提问by user2580401
hi I have something like this:
嗨，我有这样的事情：
saved = getSharedPreferences("searches", MODE_PRIVATE);
String[] mystring = saved.getAll().keySet().toArray(new String[0]);
why do we need the argument new String[0]inside toArray?
为什么我们需要new String[0]里面的参数toArray？
采纳答案by Rohit Jain
So that you get back a String[]. The one without any argument gives back to you an Object[].
以便您取回String[]. 没有任何争论的人会给你一个Object[].
See you have 2 versions of this method:
看看你有这个方法的 2 个版本：
By passing String[]array, you are using the generic version.
通过传递String[]数组，您使用的是通用版本。
A better way to pass the String[]array would be to initialize it with the size of the Set, and not with size 0, so that there is not need to create a new array in the method:
传递String[]数组的更好方法是使用 的大小初始化它Set，而不是大小为 0，这样就不需要在方法中创建新数组：
Set<String> set = saved.getAll().keySet();
String[] mystring = set.toArray(new String[set.size()]);
回答by AdamSpurgin
It's to provide a type for the return and prevent any compile-time ambiguity.
它是为返回提供类型并防止任何编译时歧义。
the signiture for that method call is: <T> T[] toArray(T[] a)
该方法调用的签名是： <T> T[] toArray(T[] a)
wheras the empty parameter one is Object[] toArray()
而空参数之一是 Object[] toArray()
