I have read in Wikipedia and have also Googled it, but I cannot figure out what “Backtracking Algorithm” means. I saw this solution from “Cracking the Code Interviews” and wonder why is this a backtracking algorithm? Answer “Backtracking” is a term that occurs in enumeratin…
Tag: java
High memory usage when using Hibernate
I code a server side application with java run on linux server. I use hibernate to open session to database, use native sql to query it and always close this session by try, catch, finally. My server query DB using hibernate with very high frequency. I already define MaxHeapSize for it is 3000M but it usually…
Log4J creates log file but does not write to it
I’m trying to configure log4j to log messages to a file. Right now, the file does get created with the name I provide, but the logs are not written to the file. My code: Contents of my log4j.properties file: When I run this, I get this output in the console: The file log.log does get created in my main …
Get month number from month name
I have this. How to get month number which contain in monthName variable? Thanks! Answer Use Java’s Calendar class. It can parse any given string into a valid calendar instance. Here is an example (assuming that the month is in english). You can specify the language in SimpleDateFormat: By default, Java…
How to convert a multipart file to File?
Can any one tell me what is a the best way to convert a multipart file (org.springframework.web.multipart.MultipartFile) to File (java.io.File) ? In my spring mvc web project i’m getting uploaded file as Multipart file.I have to convert it to a File(io) ,there fore I can call this image storing service(…
JPA @Version field doesn’t get incremented
I’m new to JPA and Hibernate and I have a problem with optimistic locking. I have a class which has an @Version annotated field. When I update the Entity represented by this class, the version counter does not increase. Here is my code: The class: and here is the main method: and here is what the consol…
Do I need to restart my system after setting JAVA in system environment’s path variable?
I did the following steps but java does not seem to be working for me, do I need to restart my system if yes then why? i am getting below error while running java in cmd Answer No, but you will need to close and recreate any cmd windows, running java programs, or the like. To check it’s correct, open
How to perform deeper matching of keys and values with assertj
Say I have a class like this: And later, a Map Using assertj, what is the best way to test that characterAges includes the “Frodo” character? For the age, I can do: And I know I could do: But then I lose my fluency. What I really want it something like this: Or even better, so that I can make
JAVA RMI wrong return type generated by WSimport tool
I am building a web service that includes some methods to do a specific job here is one of the web inferface methods: @WebMethod public DatingUserInfo[] GetAll(String gender); this method should …
Using Intellij to select block between parentheses () or brackets [] or curly brackets {} either with keyboard or mouse
I’ve started working with IntelliJ and I really like it, but there are a few features which I miss compared with Eclipse. One of which is selecting blocks between {}, (), or [] or jumping between the opening/closing of a block. For example, in eclipse if you double click just after an opening parenthese…