Java List
In Java, a list is an ordered collection of elements. The Java Collections Framework provides several classes and interfaces for working with lists. Here are some of the key classes and interfaces related to lists in Java:
-
List Interface: The
java.util.Listinterface is the primary interface for working with lists. It extends theCollectioninterface and defines methods for adding, accessing, modifying, and removing elements in a list. Some common methods includeadd,get,set,remove, andsize. -
ArrayList: The
java.util.ArrayListclass is a commonly used implementation of theListinterface. It is a dynamic array that can grow or shrink in size as elements are added or removed.ArrayListprovides fast random access to elements but may have slower insertions and deletions in the middle of the list.
List<String> arrayList = new ArrayList<>();
arrayList.add("Item 1");
arrayList.add("Item 2");
arrayList.add("Item 3");
- LinkedList: The
java.util.LinkedListclass is another implementation of theListinterface. It is based on a doubly-linked list data structure.LinkedListprovides fast insertions and deletions in the middle of the list but may have slower random access to elements.
List<String> linkedList = new LinkedList<>();
linkedList.add("Node 1");
linkedList.add("Node 2");
linkedList.add("Node 3");
- Vector: The
java.util.Vectorclass is similar toArrayListbut is synchronized, making it thread-safe. However, due to synchronization, it may have lower performance in multi-threaded environments.
List<String> vector = new Vector<>();
vector.add("Element 1");
vector.add("Element 2");
vector.add("Element 3");
- CopyOnWriteArrayList: The
java.util.concurrent.CopyOnWriteArrayListclass is a thread-safe version ofArrayList. It ensures that the list remains immutable during iteration, making it suitable for scenarios where concurrent reading is common.
List<String> copyOnWriteList = new CopyOnWriteArrayList<>();
copyOnWriteList.add("Value 1");
copyOnWriteList.add("Value 2");
copyOnWriteList.add("Value 3");
- Arrays.asList(): You can convert an array into a list using the
java.util.Arrays.asList()method.
String[] array = {"A", "B", "C"};
List<String> listFromArray = Arrays.asList(array);
- Immutable Lists: Libraries like Guava and Java 9+ provide immutable list implementations that cannot be modified after creation. These are useful for creating read-only lists.
List<String> immutableList = ImmutableList.of("Apple", "Banana", "Cherry");
When choosing a list implementation in Java, consider your specific requirements, such as the expected size of the list, the type of operations you’ll perform (e.g., random access, insertions, deletions), and whether thread safety is necessary. Each list implementation has its strengths and trade-offs, so choose the one that best suits your use case.
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