java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.String;

arrays, dictionary, java

Solution

`toArray()` returns an `Object[]`, regardless of generics. You could use the overloaded variant instead:

String[] str = map1.keySet().toArray(new String[map1.size()]);

Alternatively, since a `Set`'s `toArray` method gives no guarantee about the order, and all you're using the array for is printing out the values, you could iterate the `keySet()` directly:

for (String str: map1.keySet()) {
    System.out.println(str);
}

EDIT: Just to complete the picture, in Java 8, the `foreach` method can be used to make the code more elegant:

map1.keySet().forEach(System.out::println);

Problem

I need convert HashMap to a String array, follow is my java code ``` import java.util.HashMap; import java.util.Map; public class demo { public static void main(String[] args) { Map<String, String> map1 = new HashMap<String, String>(); map1.put("1", "1"); map1.put("2", "2"); map1.put("3", "3"); String[] str = (String[]) map1.keySet().toArray(); for(int i=0; i<str.length;i++) { System.out.println(str[i]); } } } ``` when I run the code, I get the following `ClassCastException`. ``` Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.String; at demo.main(demo.java:17) ```

Original source