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Apache Spark 2.x for Java Developers

You're reading from  Apache Spark 2.x for Java Developers

Product type Book
Published in Jul 2017
Publisher Packt
ISBN-13 9781787126497
Pages 350 pages
Edition 1st Edition
Languages
Authors (2):
Sourav Gulati Sourav Gulati
Profile icon Sourav Gulati
Sumit Kumar Sumit Kumar
Profile icon Sumit Kumar
View More author details

Table of Contents (19) Chapters

Title Page
Credits
Foreword
About the Authors
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
1. Introduction to Spark 2. Revisiting Java 3. Let Us Spark 4. Understanding the Spark Programming Model 5. Working with Data and Storage 6. Spark on Cluster 7. Spark Programming Model - Advanced 8. Working with Spark SQL 9. Near Real-Time Processing with Spark Streaming 10. Machine Learning Analytics with Spark MLlib 11. Learning Spark GraphX

Lexical scoping


Lexical scoping is also referred to as Static scoping. As per lexical scoping, a variable will be accessible in the scope in which it is defined. Here, the scope of the variable is determined at compile time.

Let us consider the following example:

public class LexicalScoping { 
   int a = 1; 
   // a has class level scope. So It will be available to be accessed 
   // throughout the class 
 
   public void sumAndPrint() { 
      int b = 1; 
      int c = a + b; 
      // b and c are local variables of method. These will be accessible 
      // inside the method only 
   } 
   // b and c are no longer accessible 
} 

Variable a will be available throughout the class (let's not consider the difference of static and non-static as of now). However, variables b and c will be available inside the sumAndPrint method only.

Similarly, a variable given inside lambda expressions are accessible only to that Lambda. For example:

list.stream().map(n -> n*2 ); 

Here n is lexically scoped to...

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