Modern Java - A Guide to Java 8

Prerequisites

• Java Development Kit (JDK) 8 or later - This tutorial requires Java 8 or newer to run the examples
• Java IDE (optional but recommended) - Any Java IDE like IntelliJ IDEA, Eclipse, or NetBeans
• Maven (optional) - For building and managing dependencies if you want to use the project structure

Installation

1. Clone the repository:

   git clone https://github.com/winterbe/java8-tutorial.git
   cd java8-tutorial
   

2. Verify Java installation:

   java -version
   javac -version
   

3. Set up your IDE (if using one):

   • Import the project as a Maven project
   • Configure the JDK to use Java 8 or later

Configuration

This is a tutorial project with no external dependencies or configuration required. The examples are self-contained and use only standard Java libraries.

If you want to run specific examples:

• Nashorn JavaScript engine: Available in JDK 8-14 (deprecated in JDK 11, removed in JDK 15+)
• File operations: Ensure you have read/write permissions in the project directory
• Path references: Some examples reference files in the res/ directory (e.g., res/nashorn1.js)

Build & Run

Running Individual Examples

Most examples are structured as standalone Java classes with a main method. To run them:

1. Using an IDE:

   • Open the desired Java file (e.g., Streams5.java, Nashorn11.java)
   • Run the main method directly

2. Using command line:

   # Compile the specific file
   javac -cp . src/com/winterbe/java8/samples/stream/Streams5.java
   
   # Run the compiled class
   java -cp . com.winterbe.java8.samples.stream.Streams5
   

Running Multiple Examples

The tutorial is designed to be run example by example. Each class contains multiple test methods (commented out by default). To run a specific test:

1. Uncomment the desired test method in the main method
2. Comment out the others
3. Run the class

Example from Streams5.java:

public static void main(String[] args) {
    List<String> strings = Arrays.asList("d2", "a2", "b1", "b3", "c");
    test8(strings);  // Uncomment this line to run test8
}

Deployment

This is a tutorial/learning project, not a deployable application. However, if you want to share or host the examples:

Options:

1. GitHub Pages - Create a documentation site with runnable examples
2. Jupyter Notebooks - Convert examples to interactive notebooks
3. Educational Platform - Deploy as part of a Java learning course

For Production Java Applications:

If you're building on the concepts learned here:

1. Build with Maven:

   mvn clean compile package
   

2. Deploy to:

   • Cloud Platforms: Heroku, AWS Elastic Beanstalk, Google App Engine
   • Container Services: Docker + Kubernetes, AWS ECS, Google Cloud Run
   • Traditional Servers: Tomcat, Jetty, WildFly

Troubleshooting

Common Issues and Solutions

1. Java Version Compatibility

• Issue: Code doesn't compile with Java 8
• Solution: Ensure you're using JDK 8 or later. Some features may require newer versions.

2. Nashorn Engine Not Found

• Issue: javax.script or Nashorn classes not found
• Solution: Nashorn was deprecated in JDK 11 and removed in JDK 15+. Use JDK 8-10 for Nashorn examples.

3. File Path Issues

• Issue: File not found exceptions when running file examples
• Solution: Ensure the res/ directory exists and contains the required files. Use absolute paths if needed.

4. Compilation Errors

• Issue: Syntax errors or missing imports
• Solution: Check that you're using the correct Java version and that all necessary imports are present.

5. Stream Operations Not Working

• Issue: Stream operations throwing exceptions
• Solution: Ensure streams are not being operated on after being closed. Streams can only be consumed once.

6. Lambda Expression Issues

• Issue: Lambda syntax errors
• Solution: Verify that the functional interface has exactly one abstract method. Use @FunctionalInterface annotation for clarity.

7. IDE Configuration

• Issue: IDE not recognizing packages or classes
• Solution: Configure the project SDK to use Java 8+, set up proper source folders, and ensure the project is imported correctly.

Debug Tips

• Use System.out.println() statements to trace execution flow
• Enable Java assertions with -ea flag for debugging
• Use your IDE's debugger to step through lambda expressions and stream operations
• Check the Java API documentation for the latest method signatures and behaviors