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Java IO - Input/Output in Java with Examples
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Java 8 Features - Complete Tutorial

Last Updated : 05 May, 2025
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Java 8 is the most awaited release of the Java programming language development because, in the entire history of Java, it has never released that many major features. It consists of major features of Java. It is a new version of Java and was released by Oracle on 18 March 2014. Java provided support for functional programming, new Java 8 APIs, a new JavaScript engine, a new Java 8 streaming API, functional interfaces, default methods, date-time API changes, etc.

Java 8 Tutorial

Major Java 8 Features Introduced

There are a few major Java 8 features mentioned below:

  • Lambda Expressions: Concise functional code using ->.
  • Functional Interfaces: Single-method interfaces.
  • Introduced and Improved APIs:
    1. Stream API: Efficient Data Manipulation.
    2. Date/Time API: Robust Date and Time Handling.
    3. Collection API Improvements: Enhanced Methods for Collections (e.g., removeIf, replaceAll).
    4. Concurrency API Improvements: New classes for parallel processing (e.g., CompletableFuture).
  • Optional Class: Handle null values safely.
  • forEach() Method in Iterable Interface: Executes an action for each element in a Collection.
  • Default Methods: Evolve interfaces without breaking compatibility.
  • Static Methods: Allows adding methods with default implementations to interfaces.
  • Method References: Refer to methods easily.

This Java 8 tutorial covers all the important Java 8 features like Java 8 APIs, Java arrays, Java 8 ArrayList, and many more included in the Java 8 programming language. To explore detail features of Java language you can explore Java course, in this course you will get a free full beginner to advanced topics of Java programming.

Java 8 Features

  • Lambda Expressions
  • Functional Interfaces
  • Method Reference
  • Streams
  • Comparable and Comparator
  • Optional Class
  • Date/Time API

Lambda Expressions

Lambda Expression basically expresses an instance of the functional interface, in other words, you can say it provides a clear and concise way to represent a method of the functional interface using an expression. Lambda Expressions are added in Java 8.

  • Lambda Expressions in Java 8
  • Lambda Expressions Parameters
  • Java Lambda Expression with Collections
  • Lambda Expression Variable Capturing with Examples
  • How to Create Thread using Lambda Expressions in Java?
  • Serialization of Lambda Expression in Java
  • Block Lambda Expressions in Java
  • Match Lambdas to Interfaces in Java
  • Converting ArrayList to HashMap in Java 8 using a Lambda Expression
  • Check if a String Contains Only Alphabets in Java Using Lambda Expression
  • Remove Elements From a List that Satisfy a Given Predicate in Java

Functional Interfaces

An interface that contains only one abstract method is known as a functional interface, but there is no restriction, you can have n number of default and static methods inside a functional interface.

  • Functional Interfaces in Java
  • Consumer Interface in Java with Examples
  • BiConsumer Interface in Java with Examples
  • Predicate Interface with Examples
  • Function Interface in Java with Examples
  • Supplier Interface in Java with Examples

Method Reference

Method reference is a shorthand notation of a lambda expression to call a method. There are four types of method references that are as follows:

  • Static Method Reference
  • Instance Method Reference of a particular object
  • Instance Method Reference of an arbitrary object of a particular type
  • Constructor Reference.

Example:

numList.stream().filter(n -> n > 5).sorted().forEach(System.out::println);
  • Method References in Java with examples
  • Converting ArrayList to HashMap using Method Reference in Java 8

Streams

Stream API is introduced in Java 8 and is used to process collections of objects with the functional style of coding using the lambda expression. So to understand what stream API is, you must have knowledge of both lambda and functional interfaces.

  • Java 8 Stream
  • Difference Between Streams and Collections in Java
  • Implement Filter Function using Reduce in Java 8 Streams
  • Java Stream API – Filters
  • Parallel vs Sequential Stream in Java
  • Functional Programming in Java 8+ using the Stream API with Example
  • Intermediate Methods of Stream in Java
  • Difference Between map() And flatMap() In Java Stream
  • Array to Stream in Java
  • 10 Ways to Create a Stream in Java
  • How to Print Elements of a Stream in Java 8
  • Collecting a Stream to an Immutable Collection in Java
  • Comparing Streams to Loops in Java
  • Why You Need to Close the Java Streams in Finally Block?
  • Convert an Iterable to Stream in Java
  • Convert an Iterator to Stream in Java
  • Difference Between Stream.of() and Arrays.stream() method in Java
  • Convert Stream to Set in Java
  • Convert a Set to Stream in Java
  • Streams on Arrays in Java 8

Java Stream Programs

Java Streams provide a powerful and expressive way to process sequences of elements in Java, enabling functional-style operations on collections of data. The Stream API, introduced in Java 8, facilitates efficient data manipulation and transformation using a sequence of operations that can be performed in parallel or sequentially

. Java Stream Programs will give a clear view to the topic:

  • Program to Convert a Map to a Stream in Java
  • Program to Convert Boxed Array to Stream in Java
  • Program to Convert Primitive Array to Stream in Java
  • Program to Convert a Set to Stream in Java using Generics
  • Program to Convert List to Stream in Java
  • Program to Convert Stream to an Array in Java
  • How to get Slice of a Stream in Java
  • Flattening Nested Collections in Java
  • How to Convert a Stream into a Map in Java
  • Find the First Element of a Stream in Java
  • Find the Last Element of a Stream in Java
  • How to Find Duplicate Elements in a Stream in Java
  • Count the Occurrence of a Given Character in a String Using Stream API in Java
  • Reverse Elements of a Parallel Stream in Java
  • How to Get ArrayList From Stream in Java 8
  • Generate Infinite Stream of Double in Java
  • Generate Infinite Stream of Integers in Java
  • Program to Iterate over a Stream with Indices in Java 8
  • Flatten a Stream of Arrays in Java using forEach loop
  • Flatten a Stream of Lists in Java using forEach loop
  • Flatten a Stream of Map in Java using forEach loop
  • Convert a String to a List of Characters in Java
  • Initialize a List in a Single Line with a Specified Value using Java Stream

Java Stream Methods

Methods related to one of the most powerful features of Java Stream are mentioned below.

  • Stream forEach() method in Java with Examples
  • Stream forEachOrdered() Method in Java with Examples
  • foreach() loop vs Stream foreach() vs Parallel Stream foreach()
  • Stream of() method in Java
  • Java Stream findAny() with Examples
  • Stream anyMatch() in Java with Examples
  • Stream allMatch() in Java with Examples
  • Stream filter() in Java with Examples
  • Stream sorted (Comparator comparator) Method in Java
  • Stream sorted() in Java
  • Stream.distinct() in Java
  • Stream.concat() in Java
  • Stream.reduce() in Java with Examples
  • stream.limit() method in Java
  • Stream ofNullable(T) method in Java with Examples
  • Stream dropWhile() method in Java with Examples
  • Stream iterate(T,Predicate,UnaryOperator) Method in Java with Examples
  • Stream takeWhile() method in Java with Examples
  • concat() Method of Stream Interface in Java API
  • Stream findFirst() in Java with Examples
  • DoubleStream mapToObj() in Java
  • Stream.Builder accept() Method in Java
  • IntStream.Builder add() Method in Java
  • DoubleStream.Builder build() in Java
  • Stream.Builder build() in Java
  • Collectors.joining() Method with Examples
  • Stream builder() in Java with Examples
  • Stream empty() in Java with Examples
  • LongStream flatMap(LongFunction mapper) in Java
  • LongStream filter() in Java with Examples

Comparable and Comparator

Comparable and Comparator are interfaces used to order objects. They are particularly useful in sorting operations and collections that require natural ordering. Here we will learn about Comparable and Comparator in depth.

  • Comparable vs Comparator in Java
  • Comparator Interface in Java with Examples
  • Why to Use Comparator Interface Rather than Comparable Interface in Java?
  • Sort an Array of Triplet using Java Comparable and Comparator
  • Java Program to Sort LinkedList using Comparable
  • How to Sort HashSet Elements using Comparable Interface in Java?
  • Sort LinkedHashMap by Values using Comparable Interface in Java
  • Sort LinkedHashMap by Keys using Comparable Interface in Java
  • How to Sort LinkedHashSet Elements using Comparable Interface in Java?

Optional Class

  • Java 8 Optional Class
  • Optional ofNullable() Method in Java with Examples
  • Optional orElse() Method in Java with Examples
  • Optional ifPresentOrElse() Method in Java with Examples
  • Optional orElseGet() Method in Java with Examples
  • Optional filter() Method in Java with Examples
  • Optional empty() Method in Java with Examples
  • Optional hashCode() Method in Java with Examples
  • Optional toString() Method in Java with Examples
  • Optional equals() Method in Java with Examples
  • Optional stream() Method in Java with examples
  • Optional or() Method in Java with Examples
  • Optional get() Method in Java with Examples
  • Optional isPresent() Method in Java with Examples
  • Optional orElseThrow() Method in Java with Examples
  • Optional of() method in Java with Examples

Date/Time API

This section gives you to handle the ever-changing world of dates and times within your Java programs. Explore working with calendars, timestamps, and time manipulation – essential skills for building applications that deal with deadlines, scheduling, or even historical data analysis.

  • Date-Time API in Java 8
  • java.time.LocalDate Class in Java
  • java.time.LocalTime Class in Java
  • java.time.LocalDateTime Class in Java
  • java.time.MonthDay Class in Java
  • java.time.OffsetTime Class in Java
  • java.time.OffsetDateTime Class in Java
  • java.time.Clock Class in Java
  • java.time.ZonedDateTime Class in Java
  • java.time.ZoneId Class in Java
  • java.time.ZoneOffset Class in Java
  • java.time.Year Class in Java
  • java.time.YearMonth Class in Java
  • java.time.Period Class in Java
  • java.time.Duration Class in Java
  • java.time.Instant Class in Java
  • Java 8 Clock instant() method with Examples
  • Java 8 Clock fixed() method with Examples

Miscellaneous

Java is a versatile and powerful programming language that encompasses a wide range of features and tools, enabling developers to build robust, high-performance applications. Let us learn some Java Miscellaneous topics are mentioned below:

  • Default Methods In Java 8
  • Static method in Interface in Java
  • Can We Override Default Method in Java?
  • forEach() method in Java
  • Nashorn JavaScript Engine in Java with Examples
  • MetaSpace in Java 8 with Examples
  • Java class dependency analyzer in Java 8 with Examples
  • LongUnaryOperator Interface in Java
  • IntUnaryOperator Interface in Java
  • DoubleUnaryOperator Interface in Java
  • UnaryOperator Interface in Java
  • ObjLongConsumer Interface with Example
  • ObjIntConsumer Interface with Example
  • ObjDoubleConsumer Interface with Example
  • DoubleSupplier Interface with Examples
  • BooleanSupplier Interface with Examples
  • IntSupplier Interface with Examples
  • LongSupplier Interface with Examples
  • LongConsumer Interface in Java with Examples
  • DoubleConsumer Interface in Java with Examples
  • IntConsumer Interface in Java with Examples
  • LongFunction Interface in Java with Examples
  • IntFunction Interface in Java with Examples
  • ToDoubleFunction Interface in Java with Examples
  • DoubleFunction Interface in Java with Examples
  • ToIntFunction Interface in Java with Examples
  • LongToIntFunction Interface in Java with Examples
  • ToLongFunction Interface in Java with Examples
  • LongToDoubleFunction Interface in Java with Examples
  • ToLongBiFunction Interface in Java with Examples
  • ToIntBiFunction Interface in Java with Examples
  • ToDoubleBiFunction Interface in Java with Examples
  • DoubleToLongFunction Interface in Java with Examples
  • IntToDoubleFunction Interface in Java with Examples
  • IntToLongFunction Interface in Java with Examples
  • DoubleToIntFunction Interface in Java with Example
  • ArrayDeque removeIf() method in Java with Examples

Conclusion

Java 8 has brought many exciting features that make it a powerful tool for developers. With the introduction of Lambda expressions, Stream API, and new Date and Time API, Java 8 has improved code efficiency and readability. These Java 8 features allow developers to write more flexible and concise code, making their work easier and more enjoyable. Overall, Java 8 continues to be a valuable update that has significantly enhanced the Java programming language.


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      Polymorphism in Java is one of the core concepts in object-oriented programming (OOP) that allows objects to behave differently based on their specific class type. The word polymorphism means having many forms, and it comes from the Greek words poly (many) and morph (forms), this means one entity ca
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    • Method Overloading in Java
      In Java, Method Overloading allows us to define multiple methods with the same name but different parameters within a class. This difference may include:The number of parametersThe types of parametersThe order of parametersMethod overloading in Java is also known as Compile-time Polymorphism, Static
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    • Overriding in Java
      Overriding in Java occurs when a subclass or child class implements a method that is already defined in the superclass or base class. When a subclass provides its own version of a method that is already defined in its superclass, we call it method overriding. The subclass method must match the paren
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    • Java Packages
      Packages in Java are a mechanism that encapsulates a group of classes, sub-packages, and interfaces. Packages are used for: Prevent naming conflicts by allowing classes with the same name to exist in different packages, like college.staff.cse.Employee and college.staff.ee.Employee.They make it easie
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    Java Interfaces

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      An Interface in Java programming language is defined as an abstract type used to specify the behaviour of a class. An interface in Java is a blueprint of a behaviour. A Java interface contains static constants and abstract methods. Key Properties of Interface:The interface in Java is a mechanism to
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    • Interfaces and Inheritance in Java
      Java supports inheritance and interfaces, which are important concepts for building reusable code. A class can extend another class and can implement one and more than one Java interface. Note: This topic has a major influence on the concept of Java and Multiple Inheritance. Interface Implementation
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    • Java Class vs Interfaces
      In Java, the difference between a class and an interface is syntactically similar; both contain methods and variables, but they are different in many aspects. The main difference is, A class defines the state of behaviour of objects.An interface defines the methods that a class must implement.Class
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    • Java Functional Interfaces
      A functional interface in Java is an interface that contains only one abstract method. Functional interfaces can have multiple default or static methods, but only one abstract method. Runnable, ActionListener, and Comparator are common examples of Java functional interfaces. From Java 8 onwards, lam
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    • Nested Interface in Java
      In Java, we can declare interfaces as members of a class or another interface. Such an interface is called a member interface or nested interface. Interfaces declared outside any class can have only public and default (package-private) access specifiers. In Java, nested interfaces (interfaces declar
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    • Marker Interface in Java
      In Java, a marker Interface is an empty interface that has no fields or methods. It is used just to mark or tag a class to tell Java or other programs something special about that class. These interfaces do not have any methods inside but act as metadata to provide information about the class. Examp
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    • Java Comparator Interface
      The Comparator interface in Java is used to sort the objects of user-defined classes. The Comparator interface is present in java.util package. This interface allows us to define custom comparison logic outside of the class for which instances we want to sort. The comparator interface is useful when
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    Java Collections

    • Collections in Java
      Any group of individual objects that are represented as a single unit is known as a Java Collection of Objects. In Java, a separate framework named the "Collection Framework" has been defined in JDK 1.2 which holds all the Java Collection Classes and Interface in it. In Java, the Collection interfac
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    • Collections Class in Java
      Collections class in Java is one of the utility classes in the Java Collections Framework. The java.util package contains the Collections class in Java. The Java Collections class is used with the static methods that operate on the collections or return the collection. All the methods of this class
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    • Collection Interface in Java
      The Collection interface in Java is a core member of the Java Collections Framework located in the java.util package. It is one of the root interfaces of the Java Collection Hierarchy. The Collection interface is not directly implemented by any class. Instead, it is implemented indirectly through it
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    • Java List Interface
      The List Interface in Java extends the Collection Interface and is a part of the java.util package. It is used to store the ordered collections of elements. In a Java List, we can organize and manage the data sequentially. Key Features:Maintained the order of elements in which they are added.Allows
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    • ArrayList in Java
      Java ArrayList is a part of the collections framework and it is a class of java.util package. It provides us with dynamic-sized arrays in Java. The main advantage of ArrayList is that, unlike normal arrays, we don't need to mention the size when creating ArrayList. It automatically adjusts its capac
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    • Vector Class in Java
      The Vector class in Java implements a growable array of objects. Vectors were legacy classes, but now it is fully compatible with collections. It comes under java.util package and implement the List interface.Key Features of Vector:It expands as elements are added.Vector class is synchronized in nat
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    • LinkedList in Java
      Linked List is a part of the Collection framework present in java.util package. This class is an implementation of the LinkedList data structure, which is a linear data structure where the elements are not stored in contiguous locations, and every element is a separate object with a data part and an
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    • Stack Class in Java
      The Java Collection framework provides a Stack class, which implements a Stack data structure. The class is based on the basic principle of LIFO (last-in-first-out). Besides the basic push and pop operations, the class also provides three more functions, such as empty, search, and peek. The Stack cl
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    • Set in Java
      The Set Interface is present in java.util package and extends the Collection interface. It is an unordered collection of objects in which duplicate values cannot be stored. It is an interface that implements the mathematical set. This interface adds a feature that restricts the insertion of duplicat
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    • Java HashSet
      HashSet in Java implements the Set interface of Collections Framework. It is used to store the unique elements and it doesn't maintain any specific order of elements. Can store the Null values.Uses HashMap (implementation of hash table data structure) internally.Also implements Serializable and Clon
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    • TreeSet in Java
      TreeSet is one of the most important implementations of the SortedSet interface in Java that uses a Tree(red - black tree) for storage. The ordering of the elements is maintained by a set using their natural ordering whether or not an explicit comparator is provided. This must be consistent with equ
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    • Java LinkedHashSet
      LinkedHashSet in Java implements the Set interface of the Collection Framework. It combines the functionality of a HashSet with a LinkedList to maintain the insertion order of elements. Stores unique elements only.Maintains insertion order.Provides faster iteration compared to HashSet.Allows null el
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    • Queue Interface In Java
      The Queue Interface is a part of java.util package and extends the Collection interface. It stores and processes the data in order means elements are inserted at the end and removed from the front. Key Features:Most implementations, like PriorityQueue, do not allow null elements.Implementation Class
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    • PriorityQueue in Java
      The PriorityQueue class in Java is part of the java.util package. It implements a priority heap-based queue that processes elements based on their priority rather than the FIFO (First-In-First-Out) concept of a Queue.Key Points:The PriorityQueue is based on the Priority Heap. The elements of the pri
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    • Deque Interface in Java
      Deque Interface present in java.util package is a subtype of the queue interface. The Deque is related to the double-ended queue that supports adding or removing elements from either end of the data structure. It can either be used as a queue(first-in-first-out/FIFO) or as a stack(last-in-first-out/
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    • Map Interface in Java
      In Java, the Map Interface is part of the java.util package and represents a mapping between a key and a value. The Java Map interface is not a subtype of the Collections interface. So, it behaves differently from the rest of the collection types.Key Features:No Duplicates in Keys: Keys should be un
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    • HashMap in Java
      In Java, HashMap is part of the Java Collections Framework and is found in the java.util package. It provides the basic implementation of the Map interface in Java. HashMap stores data in (key, value) pairs. Each key is associated with a value, and you can access the value by using the corresponding
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    • Java LinkedHashMap
      LinkedHashMap in Java implements the Map interface of the Collections Framework. It stores key-value pairs while maintaining the insertion order of the entries. It maintains the order in which elements are added.Stores unique key-value pairs.Maintains insertion order.Allows one null key and multiple
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    • Hashtable in Java
      Hashtable class, introduced as part of the Java Collections framework, implements a hash table that maps keys to values. Any non-null object can be used as a key or as a value. To successfully store and retrieve objects from a hashtable, the objects used as keys must implement the hashCode method an
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    • Java Dictionary Class
      Dictionary class in Java is an abstract class that represents a collection of key-value pairs, where keys are unique and used to access the values. It was part of the Java Collections Framework and it was introduced in Java 1.0 but has been largely replaced by the Map interface since Java 1.2.Stores
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    • SortedSet Interface in Java with Examples
      The SortedSet interface is present in java.util package extends the Set interface present in the collection framework. It is an interface that implements the mathematical set. This interface contains the methods inherited from the Set interface and adds a feature that stores all the elements in this
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    • Java Comparator Interface
      The Comparator interface in Java is used to sort the objects of user-defined classes. The Comparator interface is present in java.util package. This interface allows us to define custom comparison logic outside of the class for which instances we want to sort. The comparator interface is useful when
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    • Java Comparable Interface
      The Comparable interface in Java is used to define the natural ordering of objects for a user-defined class. It is part of the java.lang package and it provides a compareTo() method to compare instances of the class. A class has to implement a Comparable interface to define its natural ordering.Exam
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    • Java Comparable vs Comparator
      In Java, both Comparable and Comparator interfaces are used for sorting objects. The main difference between Comparable and Comparator is:Comparable: It is used to define the natural ordering of the objects within the class.Comparator: It is used to define custom sorting logic externally.Difference
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    • Java Iterator
      An Iterator in Java is an interface used to traverse elements in a Collection sequentially. It provides methods like hasNext(), next(), and remove() to loop through collections and perform manipulation. An Iterator is a part of the Java Collection Framework, and we can use it with collections like A
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