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Copying files from/to Docker container

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By rokin - January 08, 2018

docker cp foo.txt mycontainer:/foo.txt

docker cp mycontainer:/foo.txt foo.txt

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Postgres import/export table from/to CSV file

By rokin - January 08, 2018

copy tablename to '/csv.txt' delimiter ',' csv header; copy (select * from tablename) to '/csv.txt' delimiter ',' csv header; copy tablename from '/csv.txt' delimiter ',' csv header;

Math in Vim search and replace

By Unknown - November 17, 2017

In Vim, you can use function or math in search and replace. 7100,111,222,0 7100,333,444,1 7100,555,666,2 :%s/$\d*$$/\=2-submatch(1)/g 7100,111,222,2 7100,333,444,1 7100,555,666,0

Why Enum Singleton are better in Java

By Unknown - May 10, 2017

Enum Singletons are new way to implement Singleton pattern in Java by using Enum with just one instance. Though Singleton pattern in Java exists from long time Enum Singletons are relatively new concept and in practice from Java 5 onwards after introduction of Enum as keyword and feature. This article is somewhat related to my earlier post on Singleton, 10 interview questions on Singleton pattern in Java where we have discussed common questions asked on interviews about Singleton pattern and 10 Java enum examples , where we have seen how versatile enum can be. This post is about why should we use Enum as Singleton in Java , What benefit it offers compared to conventional singleton methods etc. 1) Enum Singletons are easy to write This is by far biggest advantage, if you have been writing Singletons prior ot Java 5 than you know that even with double checked locking you can have more than one instances. though that issue is fixed with Java memory model i...