import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;
public class ConvertingACollentionToAnArray {
public static void main(String[] args) {
// TODO Auto-generated method stub
List list = new LinkedList<>();
// Create an array containing the elements in a list
Object[] objectArray = list.toArray();
MyClass[] array = (MyClass[]) list.toArray(new MyClass[list.size()]);
Set set = null;
// Create an array containing the elements in a set
objectArray = set.toArray();
array = (MyClass[]) set.toArray(new MyClass[set.size()]);
Map map = null;
// Create an array containing the keys in a map
objectArray = map.keySet().toArray();
array = (MyClass[]) map.keySet().toArray(new MyClass[set.size()]);
// Create an array containing the values in a map
objectArray = map.values().toArray();
array = (MyClass[]) map.values().toArray(new MyClass[set.size()]);
}
}
class MyClass{}
Console：
这里没有给值，报空指针异常...
