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

caching/README.md

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+---
+layout: pattern
+title: Caching
+folder: caching
+permalink: /patterns/caching/
+categories: Other
+tags:
+ - Java
+ - Difficulty-Intermediate
+ - Performance
+---
+
+## Intent
+To avoid expensive re-acquisition of resources by not releasing
+the resources immediately after their use. The resources retain their identity, are kept in some
+fast-access storage, and are re-used to avoid having to acquire them again.
+
+![alt text](./etc/caching.png "Caching")
+
+## Applicability
+Use the Caching pattern(s) when
+
+* Repetitious acquisition, initialization, and release of the same resource causes unnecessary performance overhead.
+
+## Credits
+
+* [Write-through, write-around, write-back: Cache explained](http://www.computerweekly.com/feature/Write-through-write-around-write-back-Cache-explained)
+* [Read-Through, Write-Through, Write-Behind, and Refresh-Ahead Caching](https://docs.oracle.com/cd/E15357_01/coh.360/e15723/cache_rtwtwbra.htm#COHDG5177)