☕ Java 8 Basics

Welcome to the Java 8 Basics repository!
This project contains beginner-friendly Java programs and examples covering core Java concepts and Java 8 features such as Lambda Expressions, Stream API, Functional Interfaces, and more.

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🚀 Features

• ✅ Step-by-step Java examples
• 🧠 Covers Core Java + Java 8 additions
• 💬 Well-commented source code
• 🧩 Organized by topic for easy navigation
• 💻 Works with any Java 8+ setup

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📁 Repository Structure

Java8-Basics/
│
├── 01_CoreConcepts/
│   ├── HelloWorld.java
│   ├── VariablesAndDataTypes.java
│   └── ControlStatements.java
│
├── 02_Collections/
│   ├── ListExample.java
│   ├── MapExample.java
│   └── SetExample.java
│
├── 03_OOP/
│   ├── ClassAndObjects.java
│   ├── InheritanceExample.java
│   └── PolymorphismDemo.java
│
├── 04_Java8Features/
│   ├── LambdaExpressions.java
│   ├── FunctionalInterfaces.java
│   ├── StreamAPIExamples.java
│   ├── OptionalClass.java
│   └── MethodReferences.java
│
├── 05_AdditionalTopics/
│   ├── DateTimeAPI.java
│   ├── DefaultMethods.java
│   └── ForEachExample.java
│
└── README.md

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🧠 Topics Covered

🏗️ Core Java

• Variables, Data Types, and Operators
• Conditional Statements and Loops
• Arrays and Strings
• Methods and Recursion
• Exception Handling
• Object-Oriented Programming (Classes, Inheritance, Polymorphism, Encapsulation)

⚡ Java 8 Features

• Lambda Expressions
• Functional Interfaces (Predicate, Consumer, Function)
• Stream API (filter, map, reduce, collect)
• Method References (:: operator)
• Optional Class (to avoid NullPointerException)
• New Date and Time API (java.time)
• Default and Static Methods in Interfaces
• ForEach and Internal Iteration

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🛠️ Getting Started

Prerequisites

• Java JDK 8 installed
  👉 Download Java SE 8
• Set the JAVA_HOME environment variable
• Add the JDK bin folder to your system PATH
• Use any IDE or editor:
  • IntelliJ IDEA
  • Eclipse
  • VS Code

Running the Programs

# Compile
javac HelloWorld.java

# Run
java HelloWorld

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💡 Quick Java 8 Examples

🔹 1. Lambda Expression

@FunctionalInterface
interface Greeting {
    void sayHello(String name);
}

public class LambdaExample {
    public static void main(String[] args) {
        Greeting greet = name -> System.out.println("Hello, " + name + "!");
        greet.sayHello("Java 8");
    }
}

🧩 Output:

Hello, Java 8!

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🔹 2. Functional Interface with Predicate

import java.util.function.Predicate;

public class PredicateExample {
    public static void main(String[] args) {
        Predicate<Integer> isEven = n -> n % 2 == 0;
        System.out.println(isEven.test(10)); // true
        System.out.println(isEven.test(5));  // false
    }
}

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🔹 3. Stream API (filter + map + collect)

import java.util.*;
import java.util.stream.Collectors;

public class StreamExample {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Alice", "Bob", "Charlie", "David");

        List<String> filtered =
            names.stream()
                 .filter(name -> name.startsWith("C"))
                 .map(String::toUpperCase)
                 .collect(Collectors.toList());

        System.out.println(filtered); // [CHARLIE]
    }
}

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🔹 4. Optional Class

import java.util.Optional;

public class OptionalExample {
    public static void main(String[] args) {
        Optional<String> name = Optional.ofNullable(null);
        System.out.println(name.orElse("Unknown")); // prints "Unknown"
    }
}

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🔹 5. New Date and Time API

import java.time.*;

public class DateTimeExample {
    public static void main(String[] args) {
        LocalDate today = LocalDate.now();
        LocalTime time = LocalTime.now();
        LocalDateTime dateTime = LocalDateTime.now();

        System.out.println("Date: " + today);
        System.out.println("Time: " + time);
        System.out.println("DateTime: " + dateTime);
    }
}

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🔹 6. Method References

import java.util.*;

public class MethodReferenceExample {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Java", "Python", "C++");
        names.forEach(System.out::println);
    }
}

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🧪 Example Output

Hello, Java 8!
true
false
[CHARLIE]
Unknown
Date: 2025-10-15
Time: 12:30:45.678
DateTime: 2025-10-15T12:30:45.678
Java
Python
C++