Java.util Package in Java (original) (raw)

Last Updated : 08 Nov, 2025

The java.util package is one of the most widely used packages in the Java programming language. It provides a set of utility classes that support data structures, date and time manipulation, random number generation, event handling, and other commonly used functionalities in Java programs.

Provides a rich Collection Framework (List, Set, Map) for data handling.
Includes utility classes (Collections, Arrays) for sorting and searching.
Offers Date, Calendar, and Random for time and random operations.
Supports Properties for configuration management.
Contains concurrent and legacy classes for compatibility.

java_util

java.util

Package Declaration

import java. util.*;

This single import statement allows access to all classes and interfaces inside the java.util package.

Java `

import java.util.*;

public class GFG{

public static void main(String[] args){

    // Using ArrayList
    List<String> names = new ArrayList<>();
    names.add("Alice");
    names.add("Bob");
    names.add("Charlie");

    // Using Collections utility class
    Collections.sort(names);
    System.out.println("Sorted Names: " + names);

    // Simulated user input
    String userName = "User";
    System.out.println("Hello, " + userName + "!");
}

}

Output

Sorted Names: [Alice, Bob, Charlie] Hello, User!

Commonly Used Classes and Interfaces in java.util

Category	Class / Interface	Description
Collection Framework	ArrayList, LinkedList, HashSet, TreeSet, HashMap, TreeMap	Implements data structures such as lists, sets, and maps.
Utility Classes	Collections, Arrays, Objects	Provide static methods for common tasks like sorting, searching, and null checks.
Iterator Interfaces	Iterator, ListIterator, Enumeration	Used to traverse elements in a collection.
Date and Time Classes	Date, Calendar, TimeZone, Timer, TimerTask	Handle and schedule date/time-related operations.
Random Number Generation	Random	Generates random numbers for simulations or games.
Tokenizing Strings	StringTokenizer	Splits strings into tokens based on delimiters.
User Input Handling	Scanner	Reads input from various sources like keyboard or files.
Properties and Resource Bundles	Properties, ResourceBundle	Used for configuration files and localization (internationalization).
Concurrent Collections	ConcurrentHashMap, CopyOnWriteArrayList, BlockingQueue	Thread-safe collections for multithreaded applications.

Sub-packages of java.util

Sub-Package	Purpose
java.util.concurrent	Contains thread-safe concurrent collection classes and synchronization utilities.
java.util.function	Provides functional interfaces for lambda expressions.
java.util.stream	Supports functional-style operations on streams of elements.
java.util.regex	Contains classes for regular expressions.

java.util vs java.lang

Feature	java.util Package	java.lang Package
**Purpose	Provides utility classes such as collections, date/time, and random utilities.	Contains fundamental classes essential for Java language execution.
**Common Classes	ArrayList, HashMap, Date, Collections, Scanner	String, Object, Math, System, Thread
**Import Requirement	Must be explicitly imported in a program.	Imported automatically by default in every Java program.
**Usage Type	Used for data structures, utilities, and general-purpose operations.	Used for basic language constructs and core functionality.
**Package Type	Considered a utility package.	Considered a core package.