Develop Reference

Storing values of an array on a separate file as the array values changes

So I am running some code which runs over 300k times. Each time this code runs, it returns up to 300k values. I am currently storing the results I get in an ArrayList:
List<List<Object>> thisList = new ArrayList<List<Object>();
for (int i = 0; i < 300000; i++) {
thisList.add(new ArrayList<Object>());
}
for (int i = 0; i < 300000; i++) {
List<Object> result = someCode();
for (Object obj : result) {
thisList.get(obj.id).add(obj.value);
}
}
In this code, everytime obj is obtained, it has a value obj.id which specifies the index in the List where obj.value has to be stored.
What would be the most efficient way to store the results elsewhere as the search continues? My code seems to stop working past iteration 400, most likely due to low memory issues. I have considered using a simple text document where each line represents a List<Object> but through some Googling, it seems there is no way to append to a specific line, and all suggestions seems to point towards overwriting the entire text document. I've never worked with databases before which is why I am trying to avoid that for now.
Would appreciate if someone can give me suggestions on what I could do.
Edit: Is there a method which does not use a database, where after each iteration of the outer for loop, the data can be stored?
For example, given a file which currently contains
List 0: obj.value1 obj.value2
List 1: obj.value1 obj.value4
...
List 300000: obj.value3 obj.value8
and result contains
{obj<1, 100>, obj<0, 3>, ...}
where each object is of the form obj<id, value>, the file becomes
List 0: obj.value1 obj.value2 obj.value3
List 1: obj.value1 obj.value4 obj.value100
...
List 300000: obj.value3 obj.value8

You could store it in an XML file using JAXB api
Here is a link with a little tutorial on JAXB:
https://dzone.com/articles/using-jaxb-for-xml-with-java
Or you could also store it in a JSON file usin json-simple api
Here's another little tutorial:
https://stackabuse.com/reading-and-writing-json-in-java/
These are the links to download JAXB and json-simple from maven:
JAXB: https://mvnrepository.com/artifact/javax.xml.bind/jaxb-api
json-simple: https://mvnrepository.com/artifact/com.googlecode.json-simple/json-simple
Hope it'll be useful to you

how to list all the indices' name of elasticsearch using java?

In my elasticsearch I want to get all the indices' name of the cluster. How can I do using java?
I search the internet but there's no much useful information.

You can definitely do it with the following simple Java code:
List<IndexMetaData> indices = client.admin().cluster()
.prepareState().get().getState()
.getMetaData().getIndices();
The list you obtain contains the details on all the indices available in your ES cluster.

You can use:
client.admin().indices().prepareGetIndex().setFeatures().get().getIndices();
Use setFeatures() without parameter to just get index name. Otherwise, other data, such as MAPPINGS and SETTINGS of index, will also be returned by default.

Thanks for #Val's answer. According to your method, I use it in my projects, the code is:
ClusterStateResponse response = transportClient.admin().cluster() .prepareState()
.execute().actionGet();
String[] indices=response.getState().getMetaData().getConcreteAllIndices();
This method can put all the indices name into a String array. The method works.
there's another method I think but not tried:
ImmutableOpenMap<String, MappingMetaData> mappings = node.client().admin().cluster()
.prepareState().execute().actionGet().getState().‌getMetaData().getIndices().
then, we can get the keys of mappings to get all the indices.
Thanks again!

Create MultiSelectedListPreference using ArrayList

I'm trying to create a PreferenceActicity.
I need that on of my preferences will be of type MultiSelectedListPreference.
I found this code on the internet:
<MultiSelectListPreference
android:dialogTitle="#string/mode_repeat"
android:key="mode_repeat"
android:summary=""
android:title="#string/mode_repeat"
android:entries="#array/weekdays"
android:entryValues="#array/weekdays_values"
android:defaultValue="#array/empty_array"
/>
The problem is I'm getting the entries and entryValues in runtime.
I'm building the ArrayList while my app is running, the question is how can I set my ArrayList as the entries and as the entryValues?
Do I need to create an empty xml file, which I will re-write during the building of my list?

You wouldn't be able to change the xml in runtime. The solution for your problem is to use the methods setEntries()and setEntryValues()from the MultiSelectListPreference class.
Here's a basic code snippet:
MultiSelectListPreference repeatModePreference = (MultiSelectListPreference) findPreference(Constants. mode_repeat);
repeatModePreference.setEntries(yourEntries); // This is human-readable strings
repeatModePreference.setEntryValues(yourEntryvalues) // The value corresponding to the human-readable string
Hope this helps.

Updating a document in Solr with Java

As everybody knows, the documentation of Solrj in the wiki is pretty poor. I managed to query the index using the CommonsHttpSolrServer, but never with the Embedded version. Anyway, now I'm using the EdgeNGrams to display auto-suggestions, and I have a field "count" in my index, so that I can sort the results by the number of times people queried the element.
What I want to do now, is to be able to update this "count" field in my Java program, which should be quite easy I guess? I looked at the test files from the source code, but it's very complicated, and trying to do something similar always failed for me. Maybe by using Solrj?
Thanks for your help.
Edit:
In my java code, I have:
CoreContainer.Initializer initializer = new CoreContainer.Initializer();
CoreContainer coreContainer = initializer.initialize();
What I expect to get at this point, is the cores defines in solr.xml present in the coreContainer, but there is no core there (but defaultCoreName says collection1). My solr.xml file is the same as in the example dir:
<solr persistent="false">
<cores adminPath="/admin/cores" defaultCoreName="collection1">
<core name="collection1" instanceDir="." />
</cores>
</solr>

Modified from this test example. To add a value to Solr and then subsequently modify it you can do the following:
//add value to Solr
doc = new SolrInputDocument();
doc.addField("id", "A");
doc.addField("value", 10);
client.add(doc);
client.commit();
//query Solr
SolrQuery q = new SolrQuery("id:A");
QueryResponse r = client.query(q);
//update value
SolrDocument oldDoc = r.getResults().get(0);
SolrInputDocument newDoc = new SolrInputDocument();
newDoc.addField("id", oldDoc.getFieldValue("id");
HashMap<String, Object> map = new HashMap<String, Object>();
map.put("inc", 15);
newDoc.addField("value", map);
client.add(newDoc);
client.commit();
This increments the original 10 value to 25. You can also "add" to an existing field or simply "set" an existing value by changing what command you put what you put the in the HashMap.

I finally just store this count in Solr, then retrieve it and update it, then run an update, since it is not possible to update a single field in Solr and also the count field, which could be very handy!

Handling special characters with lucene

i haven't found the answer to my problem so I decided to write my question to get some help.
I use lucene to index the objects in computer memory(they exist only in my java code). While processing the code I index (using WhitespaceAnalyzer) the field with value objA/4.
My problem starts when I want to find it after the indexation (also using WhitespaceAnalyzer).
When i create a query obj* , I find all objects that start with obj - if i create a query objA/4 I also can find this object.
However i don't know how to find all objects starting with objA/ , when I create a query objA/* lucene is changing it to obja/* and finds nothing.
I've checked and "/" is not a special character so i dont need any "\" preceding it.
So my question is how to ask to get all objects that starts with objA/ (for example - objA/0, objA/1, objA/2, objA/3)?

Are you using QueryParser.escape(String) to escape everything correctly?

The code i'm using:
String node = "objA/*";
Query node_query = MultiFieldQueryParser.parse(node, "nodeName", new WhitespaceAnalyzer());
BooleanQuery bq = new BooleanQuery();
bq.add(node_query, BooleanClause.Occur.MUST);
System.out.println("We're asking for - " + bq);
IndexSearcher looker = new IndexSearcher(rep_index);
Hits hits = looker.search(bq);