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Most Common mistakes in Java Coding.

1. Copy & Paste

Its one of the most powerful tool and technique in the typical programmer. But at the same time its too dangerous that you ought to forgot the code according to you requirements. So always be cautious about what piece of code you are copying. Read at least two to three times to avoid the tricky for fishy things while your unit testing.

2. Exception Catch Block.

Always give priority to write some thing useful and meaning full statements in the exception catch block.It really worth when you troubling shooting the issues. Never leave this block with empty or sop's. And always throw the exception to the calling method.

3. String operations

Since String is immutable object, when you do any operation on string that results a new object. So after you do any modifications on String and do assign the string some object and use it.

4. Null pointers

Don't perform the operations on objects without checking the Object null condition. And while checking the null condition always provide 'null' key word as the first operand. e.g. if(null != object) . Especially while printing any calling any methods on an object.

5. Result Set next() operation.

Be in mindful that when ever you call operation cursor moves from one row to its next row.


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Maven Build Life Cyles

Following are the maven build life cycles.

Clean - Removes the generated files in 'target' folder.

command : mvn clean

Validate - It validates your project and verify all the necessary information is there in project or not.

mvn  valiate

Compile - It compiles your project code.

mvn compile

Package - It takes the compiled code and packaged to JAR/WAR/EAR. It also compiles your code if your code is not compiled.

mvn package

Install -   It takes the packaged code and puts in your local maven repository (M2_HOME). It also does the compile and package if these are not already been done.

mvn install

Deploy - It takes the package and puts in remote repository for sharing accross team members or for other projects.

mvn deploy

FYI - Above commands can be used as variety of combinations.
e.g. mvn clean install
mvn clean package
mvn clean compile package install

To skip the tests to run 
mvn clean install -DskipTests

NO SQL Types and vendors in market


KEY - VALUE Store  - Similar to a  MAP.
   e.g. Dynamo DB or REDIS

DOCUMENT Sore  - Similar to KEY-VALUE, value can be JSON/XML and key will be unqiuely idnetified this document.
   e.g. Coutch DB or mongoDB.

Column Store - Multi timentional table, identifying data with row and column numbers.
  e.g.  Cassandra or Apache HBase

Graph Store - Store relation between nodes (record entities). It has better transaction management
e.g. Neo4J and Orient DB.