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  When will resizing be triggered in Java HashMap?

HashMap is one of the most frequently used collection types in Java, it stores key-value pairs. Ideally it expects to use hash table which expects the data access time complexity to be O(1), however, due to hash conflicts, in reality, it uses linked list or red-black tree to store data which makes the worst case time complexity to be O(logn).  Although collections are using data structures like arrays and linked lists, unlike arrays, they will dynamically resize when there is not enough spa...

   JAVA,RESIZE,HASHMAP,THRESHOLD     2020-05-02 20:41:19

  Software Development Company Shares Its Development Process

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   CUSTOM SOFTWARE DEVELOPMENT COMPANY,SOFTWARE ARCHITECHURE,TESTING,REQUIREMENT ANALYSIS,MAINTENANCE     2016-01-21 00:13:26

  MySQL index optimization

Problem description: We need to access a very big table which has 40 million records. In the table, id is the primary key and program_id is indexed. When executing a select query: select * from program_access_log where program_id between 1 and 4000 The above query executes very slowly, we thought it was because there were too many records in the table. So we added id in the where condition to limit the search so that each time only half a million records would be read. select * fr...

   MySQL,Index search, Partition     2012-12-26 13:14:20

  Why should we drop or reduce use of MD5?

MD5 is a frequently used one-way hash algorithm, it is commonly used in following situations: Check data integrity. We take hash of the data stored in two different places and compare them. If the hash results are the same, then there is no need to check the actual data. This utilizes the collision-resistant feature. Two different data block will have little chance that their hash values will be the same. Many data service providers use such technique to check repeated data to avoild repeating...

   MD5,Vulnerability,attack     2012-09-29 04:47:49

  Work with MySQL character set and collation

For non-English websites, they often have to deal with character set and collation if they want to store data to and read data from databases with other languages. Character set tells the database which kind of character encoding scheme to use to store or read data, collation can be simply understood as a subset of character set, it tells the database how to sort data. We talk about working with character set and collation of MySQL today.  In MySQL, if we want to store Chinese, Japanese or ...

   MySQL,character set,collation,Chinese,question mark     2012-06-17 07:07:28

  Why accessing Java HashMap may cause infinite loop in concurrent environment

HashMap in Java is frequently used to handle key/value pairs. But it is not a good candidate to be used in concurrent environment where ConcurrentHashMap should be used instead. If used in concurrent environment, it may cause lots of unexpected behavior even including make the program getting into an infinite loop situation. To understand how this can happen, let's first discuss how HaspMap works internally. In this post we will use implementation of HashMap before Java 8 as example, Java 8 prov...

   JAVA,HASHMAP,INFINITE LOOP     2020-03-29 01:47:00

  Difference between localhost and 127.0.0.1

Lots of people would think what the address 127.0.0.1 is when first seeing this address. In fact, 127.0.0.1 is a loopback address which refers to the local machine. It is generally used for local testing. When typing ping 127.0.0.1 on local command console, it will send network packets to local IP/TCP layer to test whether IP/TCP works properly or not.  To those who are used to use localhost, it is actually mapped to 127.0.0.1 by default. There are hosts files in the system which store this...

   LINUX,NETWORK,LOCALHOST,127.0.0.1,LOCALHOST VS 127.0.0.1     2018-09-29 22:11:12

  Frequently used Git commands

Git configuration git config --global user.name "robbin" git config --global user.email "fankai@gmail.com" git config --global color.ui true git config --global alias.co checkout git config --global alias.ci commit git config --global alias.st status git config --global alias.br branch git config --global core.editor "mate -w" # Configure Editor to use textmate git config -l #List all configurations User's git configuration file : ~/.gitconfig Frequently used Git commands Check、add...

   Git,Command     2013-03-11 19:41:06

  Microsoft Interview Riddle Questions

Every year, many people will send their resume to Microsoft and Google. So how do these IT companies hire people? What kind of interview questions will they ask. Let's see what Microsoft asked before in this article. These questions are more focusing on how you are reasoning, not necessary your technical skills. 1.  You’ve got someone working for you for seven days and a gold bar to pay them. The gold bar is segmented into seven connected pieces. You must give them a piece of gold at...

   Microsoft,Interview question,Riddle questions,Answer     2012-03-10 04:56:48

  Java development company briefs about Lazy and Eager fetch in JPA/Hibernate

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   JAVA,JAVA DEVELOPMENT COMPANY,LAZY FETCH,EAGER FETCH,JPA,HIBERNET     2016-07-08 06:08:28

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