Interview question

What is the difference between Collections and Collection in Java? Java में Collections और Collection में क्या अंतर है?

Answer

Term	What it is
Collection	Root interface of the framework (List, Set, Queue extend it)
Collections	Utility class with static helper methods for working with collections

// Collection - the interface
Collection<String> collection = new ArrayList<>();
collection.add('A');
collection.size();

// Collections - the utility class, static methods
List<Integer> numbers = new ArrayList<>(Arrays.asList(5, 3, 1, 4, 2));

Collections.sort(numbers);              // [1, 2, 3, 4, 5]
Collections.reverse(numbers);           // [5, 4, 3, 2, 1]
Collections.max(numbers);               // 5
Collections.min(numbers);               // 1
Collections.shuffle(numbers);           // random order
int idx = Collections.binarySearch(numbers, 3);  // requires sorted list

// Creating immutable/unmodifiable collections
List<Integer> unmodifiable = Collections.unmodifiableList(numbers);
// unmodifiable.add(6);  // UnsupportedOperationException

List<Integer> emptyList = Collections.emptyList();
List<Integer> singleton = Collections.singletonList(42);

// Synchronized wrapper for thread-safety
List<Integer> syncList = Collections.synchronizedList(new ArrayList<>());

Term	क्या है
Collection	Framework का root interface
Collections	Static helper methods वाली utility class

Collection<String> collection = new ArrayList<>();
collection.add('A');
collection.size();

List<Integer> numbers = new ArrayList<>(Arrays.asList(5, 3, 1, 4, 2));

Collections.sort(numbers);
Collections.reverse(numbers);
Collections.max(numbers);
Collections.min(numbers);
Collections.shuffle(numbers);

List<Integer> unmodifiable = Collections.unmodifiableList(numbers);
// unmodifiable.add(6);  // UnsupportedOperationException

List<Integer> emptyList = Collections.emptyList();
List<Integer> syncList = Collections.synchronizedList(new ArrayList<>());

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