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Update specific location of file separated by specific character in JAVA

I am trying to do txt based database system. I'm stuck here now. What I want to do is enter the location of the data and then update it. I separate the data with this character. "|"
Structure like this:
ID |Name |Job |Phone Number
---+-----+--------+------------
55 |John |Plumber |555444
The id part is to find out which row it is in, and the name part is in the column.
data_Update(filename, id, "Name", "Bob Ross");
I want to do a function like this.

You could do it in following manner:
Read the file and for each line of text add a entry in your HashMap
Map<Integer, Map<String,Object>> personMap
Where key represent Id of the person, And Value represent mapping of field name to field value for the current entry.
In your db_update method, locate the person by id and update e.g.
personMap.get(Id).put(fieldname,value)

getKey in FoundationDB returns unexpected result

I trying to find a key in some Subspace at FoundationDB with getKey and KeySelector. In case if result exists in Subspace it works pretty well.
val key = new Tuple().add(3)
val subspace = new Subspace(new Tuple().add("test-subspace"))
tr.set(key.pack(), new Tuple().pack())
tr.set(subspace.pack(key), new Tuple().pack())
tr.getKey(KeySelector.firstGreaterOrEqual(subspace.pack(key)))
.thenApply[Tuple] { result =>
println(Tuple.fromBytes(result)) // ("test-subspace", 3)
subspace.unpack(result) // (3)
}
In the same time, if key does not exist in target subspace, it returns me key that was found in default subspace. Which is not what I expected...
val key = new Tuple().add(3)
val subspace = new Subspace(new Tuple().add("test-subspace"))
tr.set(key.pack(), new Tuple().pack())
tr.getKey(KeySelector.firstGreaterOrEqual(subspace.pack(key)))
.thenApply[Tuple] { result =>
println(Tuple.fromBytes(result)) // (3)
subspace.unpack(result) // Cannot unpack key that is not contained in subspace.
}
Also, if db empty, getKey instead of returning null, returns some weird byte array which cannot be parsed by Tuple.fromBytes.
val key = new Tuple().add("my-key")
tr.getKey(KeySelector.firstGreaterOrEqual(key.pack()))
.thenApply[Tuple] { result =>
println(result == null) // false
Tuple.fromBytes(result) // throws java.lang.IllegalArgumentException: Unknown tuple data type -1 at index 0
}
How should I handle situations when target subspaces do not contain the search result?

To add on to what Guarav said, when a key selector resolves to a key before the beginning of the database, it returns the empty key (''). If the key resolves past the end of the database, you'll get '\xff' in a normal transaction or '\xff\xff' if your transaction is allowed to read system keys. This is mentioned briefly at the end of the key selector documentation here.
As for not returning a result outside of your subspace, to do so would probably require getKey accepting a bound key parameter that restricts searches beyond that key. It doesn't currently have that parameter, but getRange does and can be used to perform the same query if you use a limit of 1. For example, you could do:
tr.getRange(KeySelector.firstGreaterOrEqual(subspace.pack(key)), subspace.range().end, 1)
In this case, the result will either have a key if one could be found in the subspace matching your key selector or will be empty if one could not. Of course, you'll also get back the value in this query.

This is expected behavior. Keyselector returns you the key that matches the condition - in this case first key that is greater or equal to the passed byte[]. You would need to check if returned key is valid as per your subspace requirement - by using subspace.contains() or any other validation on the returned key.
Same explanation for the second question- the returned key could be some special pre-existing row in the db, that is not created using tuple layer. Hence it cannot be parsed using tuple layer. You need to check for key validity by using subspace.contains or some similar check.

java: convert HashMap with dynamic keys to Bean

I'm trying to convert a large Map> to some JavaBean. The key of map corresponds to some property of JavaBean, and the value somehow is decoded to property value. So I decided to use some util for that, but don't know what will work. There are some requirements I have to this util (or framework):
all configuration must be in separate files
should be a possibility to map dynamic quantity of keys:
there is a map:
key | value
quan | n
key_1| value_1
key_2| value_2
........ | .............
key_n| value_n
where n - is any number
and the JavaBean has a List of some beans. They have a property. value_1, value_2, ... must be mapped in this property, and in the end there must be so much beans in list, as these keys and values in map.
3.. should be a possibility to set up custom decoder for property mapping, because in most cases the value in map is a List with 1 value, so I need to get the first item of list (if it's not empty).
4.. should be a possibility run some script to execute extraordinary mappings, for example:
there is a map, that is described in 2d point.
and the JavaBean has a property of type HashMap, where value_1 is mapped to Bean1 and some analogous value from input map is mapped to Bean2.
I've tried to use smooks, but when I've started, all these requirements were not clear yet and the smooks was something new, I haven't worked with it until now. So the smooks config doesn't contain the whole business-logic (because of second req.) and looks ugly, I don't like that. I can show the most ugliest fragment for 2d point:
<jb:bean beanId="javaBean" class="com.example.JavaBean" createOnElement="map">
<jb:wiring property="someBeans" beanIdRef="someBeanItems"/>
</jb:bean>
<jb:bean beanId="someBeanItems" class="java.util.ArrayList" createOnElement="map/entry">
<jb:wiring beanIdRef="someBeanItem"/>
</jb:bean>
<jb:bean beanId="someBeanItem" class="com.example.someBeanItem" createOnElement="map/entry">
<condition>map.quan[0]>0</condition>
<jb:expression property="property1">
index = map.quan[0]-1;
value = additionalProperties.property1_List[index];
map.quan[0] = map.quan[0] - 1;
return value;
</jb:expression>
</jb:bean>
Here "property1_List" is builded before executing smooks.
Now I look for something more nice and need your help: maybe you know how to make that better using smooks? Or what another frameworks for mapping can you recommend for my issue?

Converting a awk 2D array with counts into hashmap in java

I found this problem so interesting. I am using an awk 2D array that has a key,value,count of the same. and that is being printed to a file. This file is in the below format
A100|B100|3
A100|C100|2
A100|B100|5
Now I have a file like this .. My motive is to convert this file into a hash map so that the final output from the hash map is.
A100|B100|8
A100|C100|2
Just an aggregation
The challenge is, this one has 3 dimensions and not two. I did have an another file in the below format which is
D100|4
H100|5
D100|6
I easily aggregated the above as it is only 2D and I used the below code to do that
String[] fields= strLine.trim().split("\\|");
if(hashmap.containsKey(fields[0]))
{
//Update the value of the key here
hashmap.put(fields[0],hashmap.get(fields[0]) + Integer.parseInt(fields[1]));
}
else
{
//Inserting the key to the map
hashmap.put(fields[0],Integer.parseInt(fields[1]));
}
So this was quite simple for implementation.
But when it comes to 3D I have to have an another check inside.. My idea for this is to maintain a [B100,5(beanObject[5])]
Map<String,beanClassObject> hashmap=new Map<String,beanClassObject>();
secongField hash map which has been used in the code that has a mapping relation between the created ben Object subscript and the key as the second field "For instance it is "
This bean class would have the getter and setter method for the 2nd and 3rd fields of the file. I hope I am clear with this point. So the implementation of this would be
if(hashmap.containsKey(fields[0]))
{
**//Have to check whether the the particular key value pair already exists ... I dint find any method for this ... Just a normal iteration is there .. Could you ppl guide me regarding this**
//Update the value of the key here
secondFieldHashMap.get(fields[1]).COunt= secondFieldHashMap.get(fields[1]).getCOunt+ Integer.parseInt(fields[2]));
}
else
{
//Inserting the key to the map
hashmap.put(fields[0],Integer.parseInt(fields[1]));
secondFieldHashMap.get(fields[1]).COunt= Integer.parseInt(fields[2]));
}
else
{
// This meands there is no key field
// Hence insert the key field and also update the count of seconfFieldHashMap as done previously.
}
COuld you ppl please throw some ideas regarding this. Thank you

Consider using a Table available in the Google Guava libraries.

retrieving the values from the nested hashmap

I have a XML file with many copies of table node structure as below:
<databasetable TblID=”123” TblName=”Department1_mailbox”>
<SelectColumns>
<Slno>dept1_slno</Slno>
<To>dept1_to</To>
<From>dept1_from</From>
<Subject>dept1_sub</Subject>
<Body>dept1_body</Body>
<BCC>dept1_BCC</BCC>
<CC>dept1_CC</CC>
</SelectColumns>
<WhereCondition>MailSentStatus=’New’</WhereCondition>
<UpdateSuccess>
<MailSentStatus>’Yes’</MailSentStatus>
<MailSentFailedReason>’Mail Sent Successfully’</MailSentFailedReason>
</UpdateSuccess>
<UpdateFailure>
<MailSentStatus>’No’</MailSentStatus>
<MailSentFailedReason>’Mail Sending Failed ’</MailSentFailedReason>
</ UpdateFailure>
</databasetable>
As it is not an efficient manner to traverse the file for each time to fetch the details of each node for the queries in the program, I used the nested hashmap concept to store the details while traversing the XML file for the first time. The structure I used is as below:
MapMaster
Key Value
123 MapDetails
Key Value
TblName Department1_mailbox
SelectColumns mapSelect
Key Value
Slno dept1_slno
To dept1_to
From dept1_from
Subject dept1_sub
Body dept1_body
BCC dept1_BCC
CC dept1_CC
WhereCondition MailSentStatus=’New’
UpdateSuccess mapUS
MailSentStatus ’Yes’
MailSentFailedReason ’Mail Sent Successfully’
UpdateFailure mapUF
MailSentStatus ’No’
MailSentFailedReason ’Mail Sending Failed’
But the problem I’m facing now is regarding retrieving the Value part using the nested Keys. For example,
If I need the value of Slno Key, I have to specify TblID, SelectColumns, Slno in nested form like:
Stirng Slno = ((HashMap)((HashMap)mapMaster.get(“123”))mapDetails.get(“SelectColumns”))mapSelect.get(“Slno”);
This is unconvinent to use in a program. Please suggest a solution but don’t tell that iterators are available. As I’ve to fetch the individual value from the map according to the need of my program.
EDIT:my program has to fetch the IDs of the department for which there is privilege to send mails and then these IDs are compared with the IDs in XML file. Only information of those IDs are fetched from XML which returned true in comparison. This is all my program. Please help.
Thanks in advance,
Vishu

Never cast to specific Map implementation. Better use casting to Map interface, i.e.
((Map)one.get("foo")).get("bar")
Do not use casting in your case. You can define collection using generics, so compiler will do work for you:
Map<String, Map> one = new HashMap<String, Map>();
Map<String, Integer> two = new HashMap<String, Integer>();
Now your can say:
int n = one.get("foo").get("bar");
No casting, no problems.
But the better solution is not to use nested tables at all. Create your custom classes like SelectColumns, WhereCondition etc. Each class should have appropriate private fields, getters and setters. Now parse your XML creating instance of these classes. And then use getters to traverse the data structure.
BTW if you wish to use JAXB you do not have to do almost anything! Something like the following:
Unmarshaller u = JAXBContext.newInstance(SelectColumns.class, WhereCondition.class).createUnmarshaller();
SelectColumns[] columns = (SelectColumns[])u.unmarshal(in);

One approach to take would be to generate fully qualified keys that contain the XML path to the element or attribute. These keys would be unique, stored in a single hashmap and get you to the element quickly.
Your code would simply have to generate a unique textual representation of the path and store and retrieve the xml element based on the key.