I was trying to convert an ArrayList of Integer to Integer[]
Integer[] finalResult = (Integer[]) result.toArray();
but I got an exception
Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Integer;
Help me out please.
You need to use the version of toArray() that accepts a generic argument:
Integer[] finalResult = new Integer[result.size()];
result.toArray(finalResult);
or, as a one-liner:
Integer[] finalResult = result.toArray(new Integer[result.size()]);
You cannot cast List to an array, because a List is not an array. Here are two methods for converting a List<Integer> to an Integer[].
List<Integer> list = Arrays.asList(1, 2, 3);
Integer[] arr = list.toArray(new Integer[list.size()]);
Integer[] arr2 = list.stream().toArray(Integer[]::new); // Java 8 only
List.toArray() returns an Object array. Use List.toArray(T[]) instead:
Integer[] finalResult = (Integer[]) result.toArray(new Integer[result.size()]);
T[], which gets bound at compile time to Integer[].You need to initialize array. Try like this
Integer[] finalResult = new Integer[result.size()];
finalResult = result.toArray(finalResult);
you can do it in multiple ways:
1st method
List<T> list = new ArrayList<T>();
T [] countries = list.toArray(new T[list.size()]);
example:
List<String> list = new ArrayList<String>();
list.add("India");
list.add("Switzerland");
list.add("Italy");
list.add("France");
String [] countries = list.toArray(new String[list.size()]);
2nd method
Foo[] array = new Foo[list.size()];
list.toArray(array); // fill the array
3rd method
List<Integer> list = ...;
int[] array = new int[list.size()];
for(int i = 0; i < list.size(); i++) array[i] = list.get(i);
you can also find some example codes here - http://www.tutorialspoint.com/java/util/arraylist_toarray.htm or http://examples.javacodegeeks.com/core-java/util/list/java-list-to-array-example/
myArray = new String(); in the 4th method.
The answers here are using list.size() inside toArray() method for some reason which isn't needed at all. You can just pass an empty integer array with size 0.
It is simple and easy. Take a look:
List<Integer> yourList = List.of(1, 2, 3, 4, 5);
Integer[] intArray = yourList.toArray(new Integer[0]);
