all index.md files renamed to README.md for more compatibility with github

private-class-data/README.md

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+---
+layout: pattern
+title: Private Class Data
+folder: private-class-data
+permalink: /patterns/private-class-data/
+categories: Other
+tags:
+ - Java
+ - Difficulty-Beginner
+ - Idiom
+---
+
+## Intent
+Private Class Data design pattern seeks to reduce exposure of
+attributes by limiting their visibility. It reduces the number of class
+attributes by encapsulating them in single Data object.
+
+![alt text](./etc/private-class-data.png "Private Class Data")
+
+## Applicability
+Use the Private Class Data pattern when
+
+* you want to prevent write access to class data members