tutorialQ

Java - Cool Tricks and Tips

by mahidhar

Efficient Bulk Operations

Using addAll: Add multiple elements to a collection in one go.

java
List players = new ArrayList<>(Arrays.asList("Player1", "Player2", "Player3"));
Using removeAll and retainAll: Remove or retain elements in bulk.

Using removeAll: Remove multiple elements from a collection in one go.

java
List teamA = new ArrayList<>(Arrays.asList("Alice", "Bob", "Charlie"));
List teamB = new ArrayList<>(Arrays.asList("Bob", "Dave"));

teamA.removeAll(teamB); // Removes "Bob"
// teamA now contains "Alice", "Charlie"

teamA.retainAll(teamB); // Retains elements also in teamB
// teamA now contains "Bob"

Using Lambda Expressions with Collections
ForEach with Lambda:

java
List players = Arrays.asList("Serena", "Venus", "Naomi");
players.forEach(player -> System.out.println(player));

Removing elements conditionally:

java
List scores = new ArrayList<>(Arrays.asList("10", "20", "30", "10"));
scores.removeIf(score -> score.equals("10"));
// scores now contains ["20", "30"]

Using Streams for Advanced Operations
Filtering and Collecting:

java
List names = Arrays.asList("John", "Jane", "Jack");
List filteredNames = names.stream()
.filter(name -> name.startsWith("J"))
.collect(Collectors.toList());

Finding the maximum or minimum:

java
List scores = Arrays.asList(10, 20, 30, 40);
int maxScore = scores.stream().max(Integer::compare).orElse(-1);

Practical Tips
Choosing the Right Collection:

  • Use ArrayList for fast random access.
  • Use LinkedList for frequent insertions/deletions.
  • Use HashMap for key-value pairs with fast lookup.
  • Use TreeSet or TreeMap when you need sorted collections.

Avoiding ConcurrentModificationException:

  • Use CopyOnWriteArrayList for iterating over a list that might be modified concurrently.
  • Use ConcurrentHashMap for maps accessed by multiple threads.

Optimizing Performance:

  • Preallocate ArrayList size if the size is known in advance to reduce resizing overhead.
  • Use EnumSet and EnumMap for enum types to get efficient and fast operations.

Conclusion
Enhancing your Java collections tutorial with these additional sections will not only make it more comprehensive but also more engaging and valuable for learners. Including practical tips, interview questions, and cool tricks will cater to both beginners and advanced users, helping them understand and leverage Java collections more effectively.