Tushar Goel

Very strange it works fine for H2 database but when i use postgress it doesn't work. I only changed properties file and no other changes done

Hi

Could you please help me to solve one JPA issue? I trying to make 1 project for learning but struck here.

I have 3 entities with OneToMany relation like below:

1) Class Period {           @Id        private int periodId;       private LocalDate  startDate;       private LocalDate endDate;        @OneToMany(.., mappedBy="period")        Set<Tag> tags;   } 2)  Class Tag {          @Id        private int tagId;        @OneToMany(.. , mappedBy = "tag")        Set<Transaction> transactions;      @ManyToOne      private Period period;   } 3)  class Transaction {    @Id     private int transactionId;      @ManyToOne      private Tag tag; }

Now What i want is for a particular period i want to fetch all the related tags and all the related transactions. But whenever i query it always return Period and Tag but transactions is empty.

This query returns only period/tag. Transaction are empty.

"from Period where startDate = :start and endDate =: endDate" {   {         period  {              tags: {                   tag: {                         transactions: []          //empty here. It should show value                  }             }          }   }
But when i used join than it will fetch values in pairs

 "from Period pd, Tag tag, Transaction tr  JOIN pd.tags JOIN tag.transactions JOIN tr where startDate = :start and endDate =: endDate and pd = tag.period and tag  = transaction.tag"   like: {   {   period -1   },   {   tag -1  },   {   transaction -1 },   {   period -1  },   {   tag -1  },   {   transaction-2 }, }

I want result like 1 with transactions value. Please help me.

this multiply the result with n factorial..

so, if you have say n = 3, result = 2 in that case it calculates 3! (factorial) and multiply it with 2.

Vaibhav Gargs wrote:We have to cache some data to improve the performance. The application will be deployed in multiple clusters. Which cache will be better to use here: Redis or Memcache?

Do you want to persist the cached data in storage as well. If yes, i think Redis is the option. Memcache is pure cache, it doesn't provide feature of persisting data.

Campbell Ritchie wrote:Please provide more details; the screenshots aren't opening correctly.

I guess someone corrected or it got automatically corrected.. Thanks whoever did this.

Liutauras Vilda wrote:@OP

Are you able to share the interview question details as well as your solution? Please double check in their policy.

no policies was mentioned.

Hi,

Recently i have given an interview in which i asked to design a system (as per screenshot).. I am unable to design and failed to think from where to start.. can anyone suggest?

Or you can see on my github link

Does updating version number here `<version>1.3.3.RELEASE</version>` and here `<version>4.2.5.RELEASE</version>` for the dependency good enough to use the latest version of Spring boot? OR is it going to break things?

Yes by updating to higher version may break things.

you need to add spring-web dependency

<!-- https://mvnrepository.com/artifact/org.springframework/spring-web -->
<dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-web</artifactId>
   <version>5.1.0.RELEASE</version>
</dependency>

Stephan van Hulst wrote:
strings.collect(
 Collectors.groupingBy(
   string -> Arrays.asList(
     string.codePoints().sorted().toArray()
   )
 )
)
[/code]

Sorry but it is giving me compilation error. What i am doing wrong here?

words.stream().collect(
            Collectors.groupingBy(
                s -> Arrays.asList(
                                   s.codePoints().sorted.toArray()
                       )
               )
       );

actually it teaches me 1 more thing.. importance of pencil and paper before jumping over the code..

I will try next time to emulate the steps on paper first..

@Piet, Thanks for the nice and detailed explanation.. I have understood every single step you tried....

I was missing condition where i need to reset if from goes negative.. Anyway it was cool .. Thanks Again...


@Liutauras Vilda, Sorry for the confusion.. It was long time i have not involved in any serious coding.. So, i miss many points... Anyway, i am back now
and will have more discussion in coming days.. Sorry again for the confusion..

Jeanne Boyarsky wrote:Tushar,
softwares.stream()   .filter(s -> "winscp".equals(s.getSoftwareName()))   .filter(s -> s.getVersion() < 9)   .forEach(System.out::println);

So simple and i made it overly complicated... aha...

You are genius. anyway it is good learning for developing better coding.. Thanks...

So , i have updated my main method by adding some print statements. Hope it helps to understand what i am getting:

public static void main(String[] args) { String csvFile = "C:\\Users\\tgoel\\Desktop\\share\\sft.csv"; System.out.println(); List<Software> softwares = readCSV(csvFile); System.out.println("printing file contents"); System.out.println(softwares); System.out.println("------------------------"); Map<String, Map<String, List<Software>>> groupedOS = softwares.stream() .collect(Collectors.groupingBy(Software::getOsName, Collectors.groupingBy(Software::getSoftwareName))); System.out.println("printing contents of the map grouped by OS"); System.out.println(); System.out.println(groupedOS); System.out.println("------------------------"); Predicate<Software> software = s -> s.getSoftwareName().equals("winscp"); Predicate<Software> os = s -> s.getOsName() == "linux"; Predicate<Software> version = s -> s.getVersion() < 9; Collection<Map<String, List<Software>>> values = groupedOS.values(); System.out.println("printing contents of the map grouped by software"); System.out.println(); System.out.println(values); System.out.println("------------------------"); System.out.println("is there any winscp version older than 9? "); values.forEach(s-> s.values()    .stream() .forEach( v -> v.stream()  .filter(software.and(version))  .forEach(System.out::println))); }

My Software class:

class Software  { String osName; String softwareName; double version; public Software(String osName, String softwareName, double version) { this.osName = osName; this.softwareName = softwareName; this.version = version; } @Override public String toString() { return "Software [osName=" + osName + ", softwareName=" + softwareName + ", version=" + version + "]"; } //getter and setters }

The output looks like as below:


printing file contents
[Software [osName=Linux, softwareName=winscp, version=9.0], Software [osName=Linux, softwareName=winscp, version=10.0], Software [osName=Linux, softwareName=notepad++, version=11.0], Software [osName=Linux, softwareName=java, version=6.0], Software [osName=Ubuntu, softwareName=winscp, version=9.9], Software [osName=Ubuntu, softwareName=notepad++, version=11.1], Software [osName=Ubuntu, softwareName=notepad++, version=10.0], Software [osName=Ubuntu, softwareName=java, version=7.0], Software [osName=Windowa, softwareName=winscp, version=10.1], Software [osName=Windowa, softwareName=notepad++, version=10.0], Software [osName=Windowa, softwareName=java, version=8.0], Software [osName=MAC, softwareName=winscp, version=7.0], Software [osName=MAC, softwareName=notepad++, version=9.0], Software [osName=MAC, softwareName=java , version=10.0]]
------------------------
printing contents of the map grouped by OS

{Ubuntu={java=[Software [osName=Ubuntu, softwareName=java, version=7.0]], winscp=[Software [osName=Ubuntu, softwareName=winscp, version=9.9]], notepad++=[Software [osName=Ubuntu, softwareName=notepad++, version=11.1], Software [osName=Ubuntu, softwareName=notepad++, version=10.0]]},

Linux={java=[Software [osName=Linux, softwareName=java, version=6.0]], winscp=[Software [osName=Linux, softwareName=winscp, version=9.0], Software [osName=Linux, softwareName=winscp, version=10.0]], notepad++=[Software [osName=Linux, softwareName=notepad++, version=11.0]]},

Windowa={java=[Software [osName=Windowa, softwareName=java, version=8.0]], winscp=[Software [osName=Windowa, softwareName=winscp, version=10.1]], notepad++=[Software [osName=Windowa, softwareName=notepad++, version=10.0]]},

MAC={winscp=[Software [osName=MAC, softwareName=winscp, version=7.0]], java =[Software [osName=MAC, softwareName=java , version=10.0]], notepad++=[Software [osName=MAC, softwareName=notepad++, version=9.0]]}}
------------------------
printing contents of the map grouped by software in a OS

[{java=[Software [osName=Ubuntu, softwareName=java, version=7.0]], winscp=[Software [osName=Ubuntu, softwareName=winscp, version=9.9]], notepad++=[Software [osName=Ubuntu, softwareName=notepad++, version=11.1], Software [osName=Ubuntu, softwareName=notepad++, version=10.0]]},

{java=[Software [osName=Linux, softwareName=java, version=6.0]], winscp=[Software [osName=Linux, softwareName=winscp, version=9.0], Software [osName=Linux, softwareName=winscp, version=10.0]], notepad++=[Software [osName=Linux, softwareName=notepad++, version=11.0]]},

{java=[Software [osName=Windowa, softwareName=java, version=8.0]], winscp=[Software [osName=Windowa, softwareName=winscp, version=10.1]], notepad++=[Software [osName=Windowa, softwareName=notepad++, version=10.0]]},

{winscp=[Software [osName=MAC, softwareName=winscp, version=7.0]], java =[Software [osName=MAC, softwareName=java , version=10.0]], notepad++=[Software [osName=MAC, softwareName=notepad++, version=9.0]]}]
------------------------

is there any winscp version older than 9?
Software [osName=MAC, softwareName=winscp, version=7.0]

So, guys, i have just completed online course on Java 8. So to test my knowledge i got following question from my colleague:

We have a csv file in which 3 fields are their. 1) osName 2) Software 3) version

So we need to return outdated software version. User will provide the software and version name. File looks like as below:

OsName,Software,version Linux,winscp,9 Linux,winscp,10 Linux,notepad++,11 Linux,java,6 Ubuntu,winscp,9.9 Ubuntu,notepad++,11.1 Ubuntu,notepad++,10 Ubuntu,java,7 Windowa,winscp,10.1 Windowa,notepad++,10 Windowa,java,8 MAC,winscp,7 MAC,notepad++,9 MAC,java ,10


So, after spending few hours i come up with the solution but its looking very much complicated. Any idea how to improve it further:

public class outdatedVersionFinding { static List<Software> readCSV(String fileName) { String line = null; List<Software> softwares = new ArrayList<>(); try(BufferedReader reader = new BufferedReader(new FileReader(fileName))) { while ((line = reader.readLine()) != null) { if (line.contains("OsName")) continue; line = line.replaceAll("\"", ""); String []data = line.split(","); Software node = new Software(data[0], data[1], Double.parseDouble(data[2])); softwares.add(node); } } catch (IOException e) { e.printStackTrace(); } return softwares; } public static void main(String[] args) { String csvFile = "C:\\Users\\tgoel\\Desktop\\share\\sft.csv"; List<Software> softwares = readCSV(csvFile); Map<String, Map<String, List<Software>>> groupedOS = softwares.stream() .collect(Collectors.groupingBy(Software::getOsName, Collectors.groupingBy(Software::getSoftwareName))); Predicate<Software> software = s -> s.getSoftwareName().equals("winscp"); Predicate<Software> os = s -> s.getOsName() == "linux"; Predicate<Software> version = s -> s.getVersion() < 9; Collection<Map<String, List<Software>>> values = groupedOS.values(); values.forEach(s-> s.values()    .stream() .forEach( v -> v.stream()  .filter(software.and(version))  .forEach(System.out::println))); } }