Flash cards
Review the key moves
1/3
Core idea
What is the main idea behind Java Collections Class Methods?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
1Quick choice
Which statement best captures the main point of this lesson?
Collections Methods
The Collections class (in java.util ) contains several useful methods for working with collections like ArrayList , HashSet , and HashMap .
| Method | Description | Return Type |
|---|---|---|
| sort() | Sorts the list in ascending order (according to natural ordering) | void |
| binarySearch() | Searches for a key in a sorted list and returns its index (otherwise < 0 ) | int |
| reverse() | Reverses the order of elements in a list | void |
| reverseOrder() | Returns a comparator that imposes the reverse of natural ordering | Comparator |
| shuffle() | Randomly permutes the elements of a list | void |
| swap() | Swaps the elements at the specified positions in a list | void |
| frequency() | Returns the number of elements equal to the specified object | int |
| max() | Returns the maximum element of a collection (according to natural ordering) | T |
| min() | Returns the minimum element of a collection (according to natural ordering) | T |
| disjoint() | Checks if two collections have no elements in common | boolean |
| copy() | Copies all elements from one list into another | void |
| fill() | Replaces all elements of the list with the specified object | void |
| replaceAll() | Replaces all occurrences of one value with another in a list | boolean |
| unmodifiableList() | Returns an unmodifiable (read-only) view of the specified list | List |
| unmodifiableSet() | Returns an unmodifiable (read-only) view of the specified set | Set |
| unmodifiableMap() | Returns an unmodifiable (read-only) view of the specified map | Map |