Java：集合与数组转换

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public void convertCollectionToArray() {
List list = new ArrayList();
Object[] objectArray1 = list.toArray();
String[] array1 = list.toArray(new String[list.size()]);

Set set = new HashSet();
Object[] objectArray2 = set.toArray();
String[] array2 = set.toArray(new String[set.size()]);
}

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Integer[] numbers = {7, 7, 8, 9, 10, 8, 8, 9, 6, 5, 4};
// To convert an array into a Set first we convert it to a List. Next
// with the list we create a HashSet and pass the list as the constructor.
List list = Arrays.asList(numbers);
Set set = new HashSet(list);

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int[] numbers = {7, 7, 8, 9, 10, 8, 8, 9, 6, 5, 4};
int size = numbers.length;
Integer[] array = new Integer[size];
for (int i = 0; i < numbers.length; i++) {
Integer integer = numbers[i];
array[i] = integer;
}
List list = Arrays.asList(array);