Java Collections Tutorial

The usage method of Java collection classes is as follows:

1. Importing collection classes: Before using collection classes in a Java program, it is necessary to import the corresponding package, for example: import java.util.ArrayList;
2. Create a collection object: Use a collection class to create a collection object, such as ArrayList list = new ArrayList();
3. Add elements: use the add() method to add elements to the collection, for example: list.add(“element”);
4. Accessing elements: Use the get() method to retrieve the element in the collection, for example: String element = list.get(0);
5. Modify elements: Use the set() method to change elements in a set, for example: set.set(0, “newElement”);
6. Remove elements: use the remove() method to delete elements from the collection, for example: list.remove(0);
7. Iterate through a collection: Use a loop structure (such as a for loop or a foreach loop) to go through the elements in the collection, for example:

for (String element : list) {
    System.out.println(element);
}

1. Check if the set is empty: Use the isEmpty() method to determine if the set is empty, for example: boolean empty = list.isEmpty();
2. Get the size of the collection: Use the size() method to retrieve the number of elements in the collection, for example: int size = list.size();
3. Empty the collection: Use the clear() method to remove all elements from the collection, for example: list.clear();

The above are common methods of Java collection classes, different classes may have different methods and characteristics, so it’s important to choose the appropriate collection class based on specific requirements.