How do you define Java collections?

2 years ago
Benjamin Taylor
2 minutes

In Java, collections are data structures used to store multiple elements. Java offers a variety of collection classes, allowing users to choose the appropriate one based on their needs.

In order to define a collection, the corresponding collection class needs to be introduced. Some commonly used collection classes include the following:

  1. List is an ordered collection that allows duplicate elements. Common implementations include ArrayList and LinkedList.
List<String> list = new ArrayList<>();
  1. Set is an unordered collection that does not allow duplicate elements. Common implementations include HashSet and TreeSet.
Set<String> set = new HashSet<>();
  1. A map is a collection of key-value pairs, with each element containing a key and a value. Common implementation classes include HashMap and TreeMap.
Map<String, Integer> map = new HashMap<>();

When defining a set, you need to specify the type of elements in the set. For example, defining a list to store integers.

List<Integer> list = new ArrayList<>();

You can add, remove, and access elements in a collection by calling the appropriate methods. For example, adding an element to a list.

list.add(10);

You can use a loop to iterate through the elements in a collection.

for (int num : list) {
    System.out.println(num);
}

The collection class also offers many other methods that can be used as needed.

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