java.util Package in Java

The java.util package is part of java.base module. This package contains the most important APIs and classes in Java.

Contents of java.util Package

Java util package contains the following classes and APIs:

• Collections Framework
• Concurrent Classes
• Functional Interfaces
• Regex Classes
• Stream API
• ZIP API
• Internationalization Support Classes
• Service Loader
• Properties API
• Random Number Generation API
• String Parsing and Scanning
• Base64 Encoding and Decoding Classes
• Legacy Date and Time Classes
• Miscellaneous Exceptions and Utility Classes

Important Interfaces in java.util Package

Let’s look at some of the important interfaces in the java.util package.

1. Collection: The root interface of the Collections API.
2. Comparator: Used to implement sorting logic for the objects.
3. Queue and Deque: Queue and Double ended Queue
4. Iterator: implemented by the Collections classes to provide iteration logic.
5. List
6. ListIterator
7. Map
8. Set

Important Classes in java.util Package

1. ArrayList
2. Base64
3. Calendar
4. GregorianCalendar
5. Date
6. EnumMap
7. EnumSet
8. HashMap
9. HashSet
10. Hashtable
11. LinkedList
12. Optional
13. PriorityQueue
14. Properties
15. ResourceBundle
16. TreeMap
17. TreeSet

Utility Classes in java.util Package

1. Arrays
2. Collections
3. Formatter
4. Scanner
5. Random
6. Timer, TimerTask
7. UUID
8. StringJoiner
9. StringTokenizer

Exceptions in java.util Package

1. ConcurrentModificationException
2. EmptyStackException
3. IllformedLocaleException
4. InputMismatchException
5. MissingResourceException
6. NoSuchElementException
7. PatternSyntaxException
8. ZipException, JarException
9. IllegalFormatException

References:

• Java 12 API Doc