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How to add remaining batch of n elements into arrayList?

I'm currently learning to develop a simple blockchain program that reads sample data from .txt and creates a new block for every 10 transactions. I was wondering if the given sample data was 23 lines of transactions, is there a way to make a new block that consist of the last 3 transactions ?
Current Output
Block[header=Header[index=0,currHash=51aa6b7cf5fb821189d58b5c995b4308370888efcaac469d79ad0a5d94fb0432, prevHash=0, timestamp=1654785847112], tranx=null]
Block[header=Header[index=0,currHash=92b3582095e2403c68401448e8a34864e8465d0ea51c05f11c23810ec36b4868, prevHash=0, timestamp=1654785847385], tranx=Transaction [tranxLst=[alice|bob|credit|1.0, alice|bob|debit|2.0, alice|bob|debit|3.0, alice|bob|credit|4.0, alice|bob|debit|5.0, alice|bob|credit|6.0, alice|bob|debit|7.0, alice|bob|debit|8.0, alice|bob|debit|9.0, alice|bob|debit|10.0]]]
Block[header=Header[index=0,currHash=7488c600433d78e0fb8586e71a010b1d39a040cb101cc6e3418668d21b614519, prevHash=0, timestamp=1654785847386], tranx=Transaction [tranxLst=[alice|bob|credit|11.0, alice|bob|credit|12.0, alice|bob|debit|13.0, alice|bob|debit|14.0, alice|bob|credit|15.0, alice|bob|credit|16.0, alice|bob|credit|17.0, alice|bob|debit|18.0, alice|bob|credit|19.0, alice|bob|credit|20.0]]]
What I want
Block[header=Header[index=0,currHash=51aa6b7cf5fb821189d58b5c995b4308370888efcaac469d79ad0a5d94fb0432, prevHash=0, timestamp=1654785847112], tranx=null]
Block[header=Header[index=0,currHash=92b3582095e2403c68401448e8a34864e8465d0ea51c05f11c23810ec36b4868, prevHash=0, timestamp=1654785847385], tranx=Transaction [tranxLst=[alice|bob|credit|1.0, alice|bob|debit|2.0, alice|bob|debit|3.0, alice|bob|credit|4.0, alice|bob|debit|5.0, alice|bob|credit|6.0, alice|bob|debit|7.0, alice|bob|debit|8.0, alice|bob|debit|9.0, alice|bob|debit|10.0]]]
Block[header=Header[index=0,currHash=7488c600433d78e0fb8586e71a010b1d39a040cb101cc6e3418668d21b614519, prevHash=0, timestamp=1654785847386], tranx=Transaction [tranxLst=[alice|bob|credit|11.0, alice|bob|credit|12.0, alice|bob|debit|13.0, alice|bob|debit|14.0, alice|bob|credit|15.0, alice|bob|credit|16.0, alice|bob|credit|17.0, alice|bob|debit|18.0, alice|bob|credit|19.0, alice|bob|credit|20.0]]]
Block[header=Header[index=0,currHash=7488c600433d78e0fb8586e71a010b1d39a040cb101cc6e3418668d21b614520, prevHash=0, timestamp=1654785847387], tranx=Transaction [tranxLst=[alice|bob|credit|21.0, alice|bob|credit|22.0, alice|bob|debit|23.0]]]
my code:
Client app
public static void main(String[] args) throws IOException {
homework();
}
static void homework() throws IOException {
int count = 0;
Transaction tranxLst = new Transaction();
Block genesis = new Block("0");
System.out.println(genesis);
BufferedReader bf = new BufferedReader(new FileReader("dummytranx.txt"));
String line = bf.readLine();
while (line != null) {
tranxLst.add(line);
line = bf.readLine();
count++;
if (count % 10 == 0) {
Block newBlock = new Block(genesis.getHeader().getPrevHash());
newBlock.setTranx(tranxLst);
System.out.println(newBlock);
tranxLst.getTranxLst().clear();
}
}
bf.close();
}
Transaction class
public class Transaction implements Serializable {
public static final int SIZE = 10;
/**
* we will comeback to generate the merkle root ie., hash of merkle tree
* merkleRoot = hash
*/
private String merkleRoot = "9a0885f8cd8d94a57cd76150a9c4fa8a4fed2d04c244f259041d8166cdfeca1b8c237b2c4bca57e87acb52c8fa0777da";
// private String merkleRoot;
public String getMerkleRoot() {
return merkleRoot;
}
public void setMerkleRoot(String merkleRoot) {
this.merkleRoot = merkleRoot;
}
/**
* For the data collection, u may want to choose classic array or collection api
*/
private List<String> tranxLst;
public List<String> getTranxLst() {
return tranxLst;
}
public Transaction() {
tranxLst = new ArrayList<>(SIZE);
}
/**
* add()
*/
public void add(String tranx) {
tranxLst.add(tranx);
}
#Override
public String toString() {
return "Transaction [tranxLst=" + tranxLst + "]";
}
}
Block class
public class Block implements Serializable {
private Header header;
public Header getHeader() {
return header;
}
private Transaction tranx;
public Block(String previousHash) {
header = new Header();
header.setTimestamp(new Timestamp(System.currentTimeMillis()).getTime());
header.setPrevHash(previousHash);
String blockHash = Hasher.sha256(getBytes());
header.setCurrHash(blockHash);
}
/**
* getBytes of the Block object
*/
private byte[] getBytes() {
try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream(baos);) {
out.writeObject(this);
return baos.toByteArray();
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
public Transaction getTranx() {
return tranx;
}
/**
* aggregation rel
*/
public void setTranx(Transaction tranx) {
this.tranx = tranx;
}
/**
* composition rel
*/
public class Header implements Serializable {
private int index;
private String currHash, prevHash;
private long timestamp;
// getset methods
public String getCurrHash() {
return currHash;
}
public int getIndex() {
return index;
}
public void setIndex(int index) {
this.index = index;
}
public void setCurrHash(String currHash) {
this.currHash = currHash;
}
public String getPrevHash() {
return prevHash;
}
public void setPrevHash(String prevHash) {
this.prevHash = prevHash;
}
public long getTimestamp() {
return timestamp;
}
public void setTimestamp(long timestamp) {
this.timestamp = timestamp;
}
#Override
public String toString() {
return "Header [index=" + index + ", currHash=" + currHash + ", prevHash=" + prevHash + ", timestamp="
+ timestamp + "]";
}
}
#Override
public String toString() {
return "Block [header=" + header + ", tranx=" + tranx + "]";
}
}
enter code here

Instead of using a counter in the conditional statement, try ForLoop.
static void homework() throws IOException {
Transaction tranxLst = new Transaction();
Block genesis = new Block("0");
System.out.println(genesis);
BufferedReader bf = new BufferedReader(new FileReader("dummytranx.txt"));
String line = bf.readLine();
while (line != null) {
for (int i = 0; i < 10; i++) {
tranxLst.add(line);
line = bf.readLine();
if (line == null) {
break;
}
}
Block newBlock = new Block(genesis.getHeader().getPrevHash());
newBlock.setTranx(tranxLst);
System.out.println(newBlock);
tranxLst.getTranxLst().clear();
}
bf.close();
}

jsoup to get div elements with classes

I am new to Jsoup parsing and I want to get the list of all the companies on this page: https://angel.co/companies?company_types[]=Startup
Now, a way to do this is actually to inspect the page with the div tags relevant to what I need.
However, when I call the method :
Document doc = Jsoup.connect("https://angel.co/companies?company_types[]=Startup").get();
System.out.println(doc.html());
Firstly I cannot even find those DIV tags in my consol html output, (the ones which are supposed to give a list of the companies)
Secondly, even if I did find it, how can I find a certain Div element with class name :
div class=" dc59 frw44 _a _jm"
Pardon the jargon, I have no idea how to go through this.

The data are not embedded in the page but they are retrieved using subsequent API calls :
a POST https://angel.co/company_filters/search_data to get an ids array & a token named hexdigest
a GET https://angel.co/companies/startups to retrieve company data using the output from the previous request
The above is repeated for each page (thus a new token & a list of ids are needed for each page). This process can be seen using Chrome dev console in Network tabs.
The first POST request gives JSON output but the second request (GET) gives HTML data in a property of a JSON object.
The following extracts the company filter :
private static CompanyFilter getCompanyFilter(final String filter, final int page) throws IOException {
String response = Jsoup.connect("https://angel.co/company_filters/search_data")
.header("Content-Type", "application/x-www-form-urlencoded;charset=UTF-8")
.header("X-Requested-With", "XMLHttpRequest")
.data("filter_data[company_types][]=", filter)
.data("sort", "signal")
.data("page", String.valueOf(page))
.userAgent("Mozilla")
.ignoreContentType(true)
.post().body().text();
GsonBuilder gsonBuilder = new GsonBuilder();
Gson gson = gsonBuilder.create();
return gson.fromJson(response, CompanyFilter.class);
}
Then the following extracts companies :
private static List<Company> getCompanies(final CompanyFilter companyFilter) throws IOException {
List<Company> companies = new ArrayList<>();
URLConnection urlConn = new URL("https://angel.co/companies/startups?" + companyFilter.buildRequest()).openConnection();
urlConn.setRequestProperty("User-Agent", "Mozilla");
urlConn.connect();
BufferedReader reader = new BufferedReader(new InputStreamReader(urlConn.getInputStream(), "UTF-8"));
HtmlContainer htmlObj = new Gson().fromJson(reader, HtmlContainer.class);
Element doc = Jsoup.parse(htmlObj.getHtml());
Elements data = doc.select("div[data-_tn]");
if (data.size() > 0) {
for (int i = 2; i < data.size(); i++) {
companies.add(new Company(data.get(i).select("a").first().attr("title"),
data.get(i).select("a").first().attr("href"),
data.get(i).select("div.pitch").first().text()));
}
} else {
System.out.println("no data");
}
return companies;
}
The main function :
public static void main(String[] args) throws IOException {
int pageCount = 1;
List<Company> companies = new ArrayList<>();
for (int i = 0; i < 10; i++) {
System.out.println("get page n°" + pageCount);
CompanyFilter companyFilter = getCompanyFilter("Startup", pageCount);
pageCount++;
System.out.println("digest : " + companyFilter.getDigest());
System.out.println("count : " + companyFilter.getTotalCount());
System.out.println("array size : " + companyFilter.getIds().size());
System.out.println("page : " + companyFilter.getpage());
companies.addAll(getCompanies(companyFilter));
if (companies.size() == 0) {
break;
} else {
System.out.println("size : " + companies.size());
}
}
}
Company, CompanyFilter & HtmlContainer are model class :
class CompanyFilter {
#SerializedName("ids")
private List<Integer> mIds;
#SerializedName("hexdigest")
private String mDigest;
#SerializedName("total")
private String mTotalCount;
#SerializedName("page")
private int mPage;
#SerializedName("sort")
private String mSort;
#SerializedName("new")
private boolean mNew;
public List<Integer> getIds() {
return mIds;
}
public String getDigest() {
return mDigest;
}
public String getTotalCount() {
return mTotalCount;
}
public int getpage() {
return mPage;
}
private String buildRequest() {
String out = "total=" + mTotalCount + "&";
out += "sort=" + mSort + "&";
out += "page=" + mPage + "&";
out += "new=" + mNew + "&";
for (int i = 0; i < mIds.size(); i++) {
out += "ids[]=" + mIds.get(i) + "&";
}
out += "hexdigest=" + mDigest + "&";
return out;
}
}
private static class Company {
private String mLink;
private String mName;
private String mDescription;
public Company(String name, String link, String description) {
mLink = link;
mName = name;
mDescription = description;
}
public String getLink() {
return mLink;
}
public String getName() {
return mName;
}
public String getDescription() {
return mDescription;
}
}
private static class HtmlContainer {
#SerializedName("html")
private String mHtml;
public String getHtml() {
return mHtml;
}
}
The full code is also available here

Repeated Writing and Loading ArrayList of objects from a file

I have a 'Person' class where i stored data like name, surname etc. I make 5 object type Person, add them to ArrayList, and save this ArrayList to file. Next i'm loading from this file ArrayList and i have 5 person. Problem is when i want save again for example 10 object Person. When i'm loading ArrayList from file i'm getting only 5 person from first writing. If i repeat this still i will have load data from first writing to this file. How i can fix this ?
public class Data {
static List<Person> persons = new ArrayList<Person>();
public static void main(String[] args) throws IOException {
Data.savePersons(5);
Data.loadPersons();
/** Clean 'persons' array for TEST of load data */
persons.removeAll(persons);
System.out.println("\n-----------\nNext Round\n-----------\n");
Data.savePersons(10);
Data.loadPersons();
}
/** Save a couple of Person Object to file C:/data.ser */
public static void savePersons(int noOfPersonToSave) throws IOException {
FileOutputStream fout = null;
ObjectOutputStream oos = null;
/** Make 5 'Person' object and add them to ArrayList 'persons' for example */
for (int i = 0; i < noOfPersonToSave; i++) {
Person personTest = new Person("name" + i, "surname" + i, "email" +i, "1234567890" +i);
persons.add(personTest);
}
try {
fout = new FileOutputStream("C:\\data.ser", true);
oos = new ObjectOutputStream(fout);
oos.writeObject(persons);
System.out.println("Saving '" + persons.size() + "' Object to Array");
System.out.println("persons.size() = " + persons.size());
System.out.println("savePersons() = OK");
} catch (Exception ex) {
System.out.println("Saving ERROR: " + ex.getMessage());
} finally {
if (oos != null) {
oos.close();
}
}
}
/** Load previously saved a couple of Person Object in file C:/data.ser */
public static void loadPersons() throws IOException {
FileInputStream fis = null;
ObjectInputStream ois = null;
try {
fis = new FileInputStream("C:\\data.ser");
ois = new ObjectInputStream(fis);
persons = (List<Person>) ois.readObject();
//persons.add(result);
System.out.println("-------------------------");
System.out.println("Loading '" + persons.size() + "' Object from Array");
System.out.println("persons.size() = " + persons.size());
System.out.println("loadPersons() = OK");
} catch (Exception e) {
System.out.println("-------------------------");
System.out.println("Loading ERROR: " + e.getMessage());
} finally {
if (ois != null) {
ois.close();
}
}
}}
class Person implements Serializable {
private static final long serialVersionUID = 1L;
private String name;
private String surname;
private String mail;
private String telephone;
public Person(String n, String s, String m, String t) {
name = n;
surname = s;
mail = m;
telephone = t;
}
public String getName() {
return name;
}
public String getSurname() {
return surname;
}
public String getMail() {
return mail;
}
public String getTelephone() {
return telephone;
}}

new FileOutputStream("C:\\data.ser", true)
You're passing true for the append parameter. So you're appending a list of 10 persons to the file, after the already existing list of 5 people. And since you only read one list, you read the first you wrote, which contains 5 persons.
Pass false instead of true.

SMACK XEP-313 Implementation

It is necessary to attach a 0313 XEP (0.2)
http://xmpp.org/extensions/attic/xep-0313-0.2.html#sect-idp616432
in to SMACK/ASMACK.
I create PacketExtension for this.
public class Archive313 implements PacketExtension {
static final public String NAMESPACE = "urn:xmpp:mam:tmp";
static final public String ELEMENT = "result";
private String Id;
private String Queryid;
private String Stamp;
private String To;
private String From;
private String Type;
private String Body;
public Archive313(String id, String queryid, String stamp, String to, String from, String type, String body) {
Id = id;
Queryid = queryid;
Stamp = stamp;
To = to;
From = from;
Type = type;
Body = body;
}
#Override
public String getElementName() {
return ELEMENT;
}
#Override
public String getNamespace() {
return NAMESPACE;
}
#Override
public String toXML() {
return "<" + ELEMENT + " xmlns='" + NAMESPACE + "' queryid='" + Queryid + "' id='" + Id + "'>" +
"<forwarded xmlns='urn:xmpp:forward:0'>" +
"<delay xmlns='urn:xmpp:delay' stamp='" + Stamp + "'/><message to='"
+ To + "' from='" + From + "' type='" + Type + "'><body>" + Body + "</body></message></forwarded></result>";
}
public static class Archive313Provider implements PacketExtensionProvider {
#Override
public PacketExtension parseExtension(XmlPullParser xmlPullParser) throws Exception {
String tag_name = "";
String id = "";
String queryid = "";
String stamp = "";
String to = "";
String from = "";
String type = "";
String body = "";
while (xmlPullParser.getEventType() != XmlPullParser.END_DOCUMENT) {
switch (xmlPullParser.getEventType()) {
case XmlPullParser.START_TAG:
tag_name = xmlPullParser.getName();
for (int i = 0; i < xmlPullParser.getAttributeCount(); i++) {
if (tag_name != null && tag_name.equals("result")) {
if (xmlPullParser.getAttributeName(i).equals("queryid")) {
queryid = xmlPullParser.getAttributeValue(i);
}
if (xmlPullParser.getAttributeName(i).equals("id")) {
id = xmlPullParser.getAttributeValue(i);
}
}
if (tag_name != null && tag_name.equals("delay")) {
if (xmlPullParser.getAttributeName(i).equals("stamp")) {
stamp = xmlPullParser.getAttributeValue(i);
}
}
if (tag_name != null && tag_name.equals("message") && xmlPullParser.getAttributeCount() > 2) {
if (xmlPullParser.getAttributeName(i).equals("to")) {
to = xmlPullParser.getAttributeValue(i);
}
if (xmlPullParser.getAttributeName(i).equals("from")) {
from = xmlPullParser.getAttributeValue(i);
}
if (xmlPullParser.getAttributeName(i).equals("type")) {
type = xmlPullParser.getAttributeValue(i);
}
}
}
break;
case XmlPullParser.END_TAG:
tag_name = xmlPullParser.getName();
break;
case XmlPullParser.TEXT:
if ("body".equals(tag_name)) {
body = xmlPullParser.getText();
}
break;
default:
break;
}
xmlPullParser.next();
}
return new Archive313(id,queryid,stamp,to,from,type,body);
}
}
}
ProviderManager pm = ProviderManager.getInstance();
pm.addExtensionProvider("result", "urn:xmpp:mam:tmp", new Archive313.Archive313Provider());
mXMPPConnection.addPacketListener(archiveListener, new PacketExtensionFilter("result", "urn:xmpp:mam:tmp"));
private PacketListener archiveListener = new PacketListener() {
#Override
public void processPacket(Packet packet) {
Log.d("archiveListener", packet.toXML());
}
};
In this implementation I do not give any Packet to archiveListener.
If i set filter:
PacketFilter filter = new PacketFilter() {
#Override
public boolean accept(Packet packet) {
if (packet.toXML().contains("urn:xmpp:mam:tmp")) {
return true;
}
return false;
}
};
I got packages but they are not full.
Need to be:
<message id='aeb213' to='juliet#capulet.lit/chamber'>
<result xmlns='urn:xmpp:mam:tmp' queryid='f27' id='28482-98726-73623'>
<forwarded xmlns='urn:xmpp:forward:0'>
<delay xmlns='urn:xmpp:delay' stamp='2010-07-10T23:08:25Z'/>
<message to='juliet#capulet.lit/balcony'
from='romeo#montague.lit/orchard'
type='chat'>
<body>Call me but love, and I'll be new baptized; Henceforth I never will be Romeo.</body>
</message>
</forwarded>
</result>
</message>
I got:
<message id='aeb213' to='juliet#capulet.lit/chamber'>
<result xmlns='urn:xmpp:mam:tmp' queryid='f27' id='28482-98726-73623'>
</result>
</message>
In SMACK Logs I got full message.

It looks like your code
ProviderManager pm = ProviderManager.getInstance();
pm.addExtensionProvider("result", "urn:xmpp:mam:tmp", new Archive313.Archive313Provider());
never calls. Check this. Commonly, this code must be placed in static block of main class which working with xmpp lib.

To add any extension you have to do three things.
Create a custom extension class extending Extension/ExtensionElement.
Create an extension provider extending ExtensionProvider.
Add custom extension provider to provider manager.
Note : Extension provider will parse your extension from packet (XML) as per your requirement (onParse() method of provider). Every custom extension have to parsed manually and need to add custom provider to provider manager.

generating a number between a range using json

How can we generate a number between a range using Json.
Like we have to generate a number between 0 to 50, how can we perform this in Java using a Json.
This is my Json Data
{
"rand": {
"type': "number",
"minimum": 0,
"exclusiveMinimum": false,
"maximum": 50,
"exclusiveMaximum": true
}
}
This is what I have tried in Java
public class JavaApplication1 {
public static void main(String[] args) {
try {
for (int i=0;i<5;i++)
{
FileInputStream fileInputStream = new FileInputStream("C://users/user/Desktop/V.xls");
HSSFWorkbook workbook = new HSSFWorkbook(fileInputStream);
HSSFSheet worksheet = workbook.getSheet("POI Worksheet");
HSSFRow row1 = worksheet.getRow(0);
String e1Val = cellE1.getStringCellValue();
HSSFCell cellF1 = row1.getCell((short) 5);
System.out.println("E1: " + e1Val);
JSONObject obj = new JSONObject();
obj.put("value", e1Val);
System.out.print(obj + "\n");
Map<String,Object> c_data = mapper.readValue(e1Val, Map.class);
System.out.println(a);
}
} catch (FileNotFoundException e) {
} catch (IOException e) {
}
}
}
Json Data is stored in excel sheet, from there I am reading it in Java program

Get a Json-reader like GSON.
Read in the JSON to an equivalent Object like
public class rand{
private String type;
private int minimum;
private boolean exclusiveMinimum;
private int maximum;
private boolean exclusiveMaximum;
//this standard-constructor is needed for the JsonReader
public rand(){
}
//Getter for all Values
}
and after reading in your JSON you can access your Data via your getter-methods

I think that Jackson may be of help here.
I suggest that you create a data model in Java that reflects the JSON. This can along the lines of:
// This is the root object. It contains the input data (RandomizerInput) and a
// generate-function that is used for generating new random ints.
public class RandomData {
private RandomizerInput input;
#JsonCreator
public RandomData(#JsonProperty("rand") final RandomizerInput input) {
this.input = input;
}
#JsonProperty("rand")
public RandomizerInput getInput() {
return input;
}
#JsonProperty("generated")
public int generateRandomNumber() {
int max = input.isExclusiveMaximum()
? input.getMaximum() - 1 : input.getMaximum();
int min = input.isExclusiveMinimum()
? input.getMinimum() + 1 : input.getMinimum();
return new Random().nextInt((max - min) + 1) + min;
}
}
// This is the input data (pretty much what is described in the question).
public class RandomizerInput {
private final boolean exclusiveMaximum;
private final boolean exclusiveMinimum;
private final int maximum;
private final int minimum;
private final String type;
#JsonCreator
public RandomizerInput(
#JsonProperty("type") final String type,
#JsonProperty("minimum") final int minimum,
#JsonProperty("exclusiveMinimum") final boolean exclusiveMinimum,
#JsonProperty("maximum") final int maximum,
#JsonProperty("exclusiveMaximum") final boolean exclusiveMaximum) {
this.type = type; // Not really used...
this.minimum = minimum;
this.exclusiveMinimum = exclusiveMinimum;
this.maximum = maximum;
this.exclusiveMaximum = exclusiveMaximum;
}
public int getMaximum() {
return maximum;
}
public int getMinimum() {
return minimum;
}
public String getType() {
return type;
}
public boolean isExclusiveMaximum() {
return exclusiveMaximum;
}
public boolean isExclusiveMinimum() {
return exclusiveMinimum;
}
}
To use these classes the ObjectMapper from Jackson can be used like this:
public static void main(String... args) throws IOException {
String json =
"{ " +
"\"rand\": { " +
"\"type\": \"number\", " +
"\"minimum\": 0, " +
"\"exclusiveMinimum\": false, " +
"\"maximum\": 50, " +
"\"exclusiveMaximum\": true " +
"} " +
"}";
// Create the mapper
ObjectMapper mapper = new ObjectMapper();
// Convert JSON to POJO
final RandomData randomData = mapper.readValue(json, RandomData.class);
// Either you can get the random this way...
final int random = randomData.generateRandomNumber();
// Or, you can serialize the whole thing as JSON....
String str = mapper.writeValueAsString(randomData);
// Output is:
// {"rand":{"type":"number","minimum":0,"exclusiveMinimum":false,"maximum":50,"exclusiveMaximum":true},"generated":21}
System.out.println(str);
}
The actual generation of a random number is based on this SO question.