如何从 Java 中的集合中删除特定元素

Question

I have declared a specific collecion looking like this

private static String[] testCollection= new String[]
        {"DB085175AF684343888344561C2723C1",
         "DB085175AF684343888344561C2723C2"}

Then there is a method that returns a random element from my collection.

public static <T> T getRandomElement(Collection<T> collection)
{
    int size = collection.size();
    return (T) collection.toArray()[random.nextInt(size)];
}

So my question is how to remove randomly chosen element when i declare it like

String testName = CollectionUtil.getRandomElement(informationSystemName);

I can't figure out how to build a method that removes generated testName from testCollection

Answer 1

Arrays in Java have a fixed size, which is set when the array is created. You cannot remove an element from an existing array such as testCollection - you'll have to create a new array without the element that you want to remove.

This is easier if you first convert the array to a List , use the remove() method of List to remove the desired element, and then create a new array from the list with the element removed:

List<String> list = new ArrayList<>(Arrays.asList(testCollection));
list.remove(testName);
    
String[] result = list.toArray(new String[list.size()]);

Or work with List directly instead of arrays - collection classes such as List are more flexible and often more useful than arrays:

private static List<String> testCollection = List.of(
    "DB085175AF684343888344561C2723C1", "DB085175AF684343888344561C2723C2");

public static <T> T getRandomElement(List<T> collection) {
    int size = collection.size();
    return collection.get(random.nextInt(size));
}

String testName = getRandomElement(testCollection);
testCollection.remove(testName);