Stream API in Java

Introduction

• Previous video covered forEach and its usage.
• Current topic: Stream API.
• Purpose of collections in Java: To store data (integers, strings, complex objects).

Processing Data in Collections

• Methods for processing data:
  • Normal for loop
  • External for loop
  • forEach
• Operations needed:
  • Changing values
  • Filtering values
  • Reducing values

Stream API Overview

• Allows for various operations without modifying the existing list.
• Preferred for processing large amounts of data using multiple threads.

Creating a Stream

• Convert a collection to a stream: nums.stream() or nums.parallelStream().
• Streams allow for operations like map, filter, reduce etc.

Basic Stream Operations

1. Mapping Values: Example - Doubling Values

   • Use the map method: data.map(n -> n * 2)
   • Creates a new stream without modifying the original list.

2. ForEach

   • Iterate over stream values.

3. Handling Streams

   • Streams can only be consumed once.
   • Example of handling exceptions when trying to reuse a consumed stream.

Stream Operations: Examples

• Count: Get the size of the stream.
• Sorted: Sort the values in the stream.
• Filter: Filter values based on a condition (e.g., even/odd numbers).
  • Example: filter(n -> n % 2 == 1) for odd numbers.
• Map: Transform each value (e.g., doubling values).
• Reduce: Combine stream values into a single result.
  • Example: Summing values: reduce(0, (acc, elem) -> acc + elem)

Stream Method Details

• Filter: Uses Predicate functional interface (filter(Predicate))
• Map: Uses Function functional interface (map(Function))
• Demonstration of using and replacing lambdas with full predicate or function objects.

Lambda Expressions

• Simplify code syntax.
• Reduction explanation: simplify down to a single concise operation.

Advanced Operations and Insights

• Streams prevent data leakage and ensure resource management.
• Methods to chain stream operations for readability and efficiency.
• Explanation of building streams using builder pattern.
• Combining multiple stream methods: stream().filter(...).map(...).forEach(...)

Conclusion

• Stream API offers efficient and readable ways to process collections.
• Benefits in large data processing with parallel streams.
• Encouragement to explore more Stream API features.