1) What is Serialization and deserialization ?
Answer:-
@https://github.com/MdGolam-Kibria/JavaBrainStore/tree/master/src/main/java/com/CrackCode/SerializationDeserialization
2)Polymorphism in java ? How can we achieve Polymorphism ?
Answer:-
@https://github.com/MdGolam-Kibria/interviewQuestion/tree/master/src/main/java/com/CrackCode/Polymorphism
4) What About Singleton pattern in java ? Types of singleton ? and How can we achieve that ?
Answer:-
@https://github.com/MdGolam-Kibria/interviewQuestion/tree/master/src/main/java/com/CrackCode/designPattern/SingletonPattern
5) Difference between factory and abstract factory pattern ?
Answer:-
@https://github.com/MdGolam-Kibria/interviewQuestion/tree/master/src/main/java/com/CrackCode/designPattern/Factory
@https://github.com/MdGolam-Kibria/interviewQuestion/tree/master/src/main/java/com/CrackCode/designPattern/abstractFactory
6) What is the Prototype Pattern ?
Answer:-
@https://github.com/MdGolam-Kibria/interviewQuestion/tree/master/src/main/java/com/CrackCode/designPattern/Prototype
7) What is the Builder Pattern ?
Answer:-
@https://github.com/MdGolam-Kibria/interviewQuestion/tree/master/src/main/java/com/CrackCode/designPattern/BuilderPattern
-
🔥🔥🔥 Java 8 All features like everything about [🦸‍♂️Stream API, 🦸‍♂️Optional class, 🦸‍♂️Functional Interface, 🦸‍♂️lambda,🦸‍♂️Predicate] 🔥🔥🔥🔥
Answer:-
@https://github.com/MdGolam-Kibria/interviewQuestion/tree/master/src/main/java/com/CrackCode/java8
9) Difference JPA and JDBC with explain details with example.
Answer:-
10) Convert Sql result array to expected JSON Object using Reflection API 🔥
Answer:-
/**
* Common method for getData from database using entity Manager
*/
@Service
public class EntityManagerQueryHelper {
@PersistenceContext
private EntityManager entityManager;
public Collection<Object> getQueryResult(String sql, Object expectedConvertedPojoClass) {
Query query = entityManager.createNativeQuery(sql);
/**
* here expectedConvertedPojoClass model must look like the [query.getResultList()] value serial
*/
return convertToModelObject(query.getResultList(), expectedConvertedPojoClass);
}
public Collection<Object> convertToModelObject(List resultList, Object expectedConvertedPojoClass) {//expectedConvertedPojoClass property should be same as your( sql output) serial value
try {
List<Object> objects = new ArrayList<>();
for (int o = 0; o < resultList.size(); o++) {
Field[] allPro = expectedConvertedPojoClass.getClass().getDeclaredFields();
Map<Object, Object> properties = new HashMap<>();
for (int i = 0; i < allPro.length; i++) {
properties.put(expectedConvertedPojoClass.getClass().getDeclaredFields()[i].getName(), ((Object[]) resultList.get(o))[i]);
}
objects.add(properties);
}
return objects;
} catch (Exception e) {
return null;
}
}
}1) What is Multithreading in java ?.
Answer:-
MULTITHREADING in Java is a process of executing two or more threads simultaneously to maximum utilization of CPU. Multithreaded applications execute two or more threads run concurrently. Hence, it is also known as Concurrency in Java. Each thread runs parallel to each other. Mulitple threads don't allocate separate memory area, hence they save memory. Also, context switching between threads takes less time.
2) Create a Thread and assign work to the thread after that get result from the thread ?.
Answer :-
3) Create two Thread and assign work to the threads after that get result from the thread ? Remember that second thread shouldn't workable before end first thread work.
Answer :-
4)Create two or more thread that should be work simultaneously
Answer :-
1)Create PL/SQL operation for get all data from a table and print some specific value
Answer :-
2)Create a procedure for insert data to a table
Answer :-
Another one Example:-
3)How to call a procedure for a spring application
Answer :-
3)Create a procedure for get all data from a table ? and call it from spring boot server
Answer :-
4)Create a procedure for get XML as IN param and parse it after that save data to a table ? and call it from spring boot server by sending the expected params
Answer :-
create procedure saveEmployeeex(
stmt IN CLOB,
output OUT number
) AS
id_T EMPLOYEE.ID%TYPE;
name_T EMPLOYEE.NAME%TYPE;
email_T EMPLOYEE.EMAIL%TYPE;
tempRow number;
CURSOR field_cursor
IS
SELECT XMLTYPE.EXTRACT(VALUE(a),
'/rowrecord/STUDENT_ID/text()').getStringVal(),
XMLTYPE.EXTRACT(VALUE(a),
'/rowrecord/STUDENT_NAME/text()').getStringVal(),
XMLTYPE.EXTRACT(VALUE(a), '/rowrecord/STUDENT_EMAIL/text()').getStringVal()
FROM TABLE (
XMLSEQUENCE(
XMLTYPE(stmt).EXTRACT('/statement/rowrecord'))) a;
begin
output := 0;
tempRow:=0;
open field_cursor;
LOOP
FETCH field_cursor
INTO id_T,name_T,email_T;
exit when field_cursor%NOTFOUND;
END LOOP;
select count(*) into tempRow from EMPLOYEE where ID = id_T;
IF tempRow is not null then
update EMPLOYEE
set EMPLOYEE.ID = id_T,
EMPLOYEE.NAME = name_T,
EMPLOYEE.EMAIL =email_T
where ID = id_T;
output := 1;
else
insert into EMPLOYEE(id, name, email) VALUES (id_T, name_T, email_T);
commit;
output := 1;
end if;
END 
5)Create a procedure inside a package using PL?SQL ? and call it from spring boot server
Answer :-
i)Create Package :-
create PACKAGE getAllEmployeeByPackage AS
PROCEDURE getAll(
e_disp OUT SYS_REFCURSOR
);
END getAllEmployeeByPackage;
/ii) create package body :-
create package body getAllEmployeeByPackage as
procedure getAll(
e_disp OUT SYS_REFCURSOR
) IS
BEGIN
open e_disp for select * from EMPLOYEE;
END getAll;
end getAllEmployeeByPackage;
/
6)Create a procedure for get Employee by id otherwise retun empty sys_refcursor from EMPLOYEE table ? and call it from spring boot server
Answer :-
procedure getEmployeeById(
id_in IN EMPLOYEE.ID%type,
e_disp OUT SYS_REFCURSOR
) IS
hasEmployee number;
BEGIN
hasEmployee := 0;
SELECT count(*) into hasEmployee from EMPLOYEE where ID = id_in;
IF hasEmployee <> 0 THEN --here <> means !=
OPEN e_disp FOR SELECT * FROM EMPLOYEE WHERE ID = id_in;
ELSE
--return empty SYS_REFCURSOR couse 1=2 not equal always
OPEN e_disp FOR SELECT * FROM EMPLOYEE WHERE 1=2;
END IF;
END getEmployeeById;
3)Create a PL/SQL function (SUM of two number) and test it from SYSTEM
Answer :-
create or replace function adder(n1 in number, n2 in number)
return number
is
n3 number(8);
begin
n3 :=n1+n2;
return n3;
end;
/
select adder(12,8) as sum from DUAL;7)Call a procedure inside a FUNCTION for get employee by ID
Answer :-
create procedure getEmployeeAllInsideFunctionCall(
empl_idd IN EMPLOYEE.ID%type,
e_disp OUT SYS_REFCURSOR
)
is
begin
e_disp := getEmployee(empl_idd);
end;
/Function :-
create function getEmployee(
emp_id EMPLOYEE.ID%type
) return SYS_REFCURSOR
is
-- hasEmployee number;
expectedEmployee SYS_REFCURSOR;
begin
-- select count(*) into hasEmployee from EMPLOYEE where ID = emp_id;
open expectedEmployee for select * from EMPLOYEE where ID = emp_id;
if SQL%FOUND then
return expectedEmployee;
end if;
if SQL%NOTFOUND then
open expectedEmployee for select * from EMPLOYEE where 4 = 6;
return expectedEmployee;
end if;
return expectedEmployee;
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE('EMPLOYEE find error');
end;
/8)Create a Sequence and use and use it as a table id and and create a view 🎥 that will return a result by joining multiple table and call the view from a procedure and call it from your application
Answer :-
CREATE SEQUENCE IncrementId
INCREMENT BY 10
START WITH 10
MINVALUE 10
MAXVALUE 100
CYCLE
CACHE 2;
CREATE TABLE Persons
(
id int,
lastName varchar(255),
fastName varchar(255),
area varchar(255),
address varchar(255)
);
CREATE TABLE PersonsProfession
(
PersonID int,
Profession varchar(255)
);
insert into PERSONS values (INCREMENTID.nextval, 'Kibria', 'Golam', 'Tejgaon', 'Dhaka');--[INCREMENTID.nextval] call the SEQUENCE here
INSERT INTO PersonsProfession values (40, 'Teacher');
INSERT INTO PersonsProfession values (50, 'Engineer');
INSERT INTO PersonsProfession values (60, 'Doctor');
create or REPLACE VIEW PersonDetails
AS
SELECT p.*, pd.*
from PERSONS p
left join PersonsProfession pd on p.ID = pd.PERSONID
order by p.ID desc;
create or replace procedure getPersonByCallingView(
id_in IN PERSONS.ID%type,
e_disp OUT SYS_REFCURSOR
) IS
hasPerson number;
BEGIN
hasPerson := 0;
SELECT count(*) into hasPerson from PERSONDETAILS pd where pd.ID = id_in;
IF hasPerson <> 0 THEN --here <> means !=
OPEN e_disp FOR SELECT * from PERSONDETAILS pd where pd.ID = id_in;
ELSE
--return empty SYS_REFCURSOR couse 1=2 not equal always
OPEN e_disp FOR SELECT * FROM EMPLOYEE WHERE 1 = 2;
END IF;
END getPersonByCallingView;9)Select column values based on condition and check if any value is null replace it as 'This is null' in Oracle
Answer :-
select CASE
when e.ID = 7 then
'This is 7'
else 'This is not seven'
end
as conditionResult,--This is one kind of conditions
decode(e.ID,22,222,55,555) as conditionalId,--This is another type of conditions(here logic is if id 22 then it shows 222 otherwise if id is 55 it will show 555 )
e.id,
NVL(NAME, 'Name is null') as nullCheckName,
email
from EMPLOYEE e;10)Parse data from json using JSON_VALUE() PL/SQL
Answer :-
JSON demo
{
"collectionType": 0,
"billInfo": {
"BANK_BRANCH_CODE": "",
"COMMISSIONARATES_CODE": "437689ewr234",
"APPELLATE_TRIBUNAL": "",
"ECONOMIC_CODE": "0601",
"APPELLTE": "",
"EMAIL": "[email protected]",
"TEL_NUMBER": "01723000033",
"APPELLTE_CODE": "",
"PERSL": "",
"TAX_PERIOD_MONTH": "November",
"AMOUNT": "21.0",
"FUNCTION_CODE": "23424",
"PURPOSE_CODE": "",
"PURPOSE_DATE": "",
"LEGAL_CODE": "1",
"TAX_TYPE_CODE": "1601",
"PURPOSE_NO": "",
"TAX_PERIOD_YEAR": "2020",
"TXT50": "",
"BIN": "34234-0503",
"VDS_OPTION": "",
"VDS_SING_BIN": "",
"TRANSACTION_TYPE": "T",
"NAME": "SUMON GARMNETS TWO",
"OPERATION_CODE": "234",
"PERIOD": "",
"ADDRESS": " 234324 kajipara; 234 PS; Chittagong-4000; Bangladesh",
"TAX_TYPE_NAME": "",
"APPELE_DESC": "",
"COMMISSIONARATES_NAME": "Large Taxpayer Unit - VAT"
},
"billerCode": "vat"
}
SELECT
AT.METADATA
FROM
CORP_APPROVED_TRANSACTION AT
WHERE
AT.METADATA IS NOT NULL
AND JSON_VALUE(AT.METADATA, '$.billerCode') = 'vat'
AND JSON_VALUE(AT.METADATA, '$.billInfo.EMAIL') = '[email protected]';
11)How to run a sql script for Multiple operation without creating procedure in oracle
Answer :-
DECLARE
cursor allCallCenterAndAllOPS
IS
select * from USERS where USER_TYPE in (6,7,2,3);
BEGIN
FOR callCenterOrOps IN allCallCenterAndAllOPS
LOOP
INSERT
INTO NOTIFICATION_COMPANY_CONFIG (
ID,
COMPANY_ID,
EVENT_ID,
IS_SMS,
IS_EMAIL,
IS_ACTIVE,
USER_ID,
CREATEDAT,
CREATEDBY,
UPDATEDAT,
UPDATEDBY,
FUTURE_STATUS,
OLD_STATUS,
REJECT_REASON)
VALUES (
NOTI_COMP_CFG_SEQ.nextval,--ID
1,--companyId
48,--eventId
0,--IS_SMS
1,--IS_EMAIL
1,--IS_ACTIVE
callCenterOrOps.ID,--USER_ID
sysdate,--CREATEDAT
null,--CREATEDBY
null,--UPDATEDAT
null,--UPDATEDBY
null,--FUTURE_STATUS
null,--OLD_STATUS
null--REJECT_REASON
);
DBMS_OUTPUT.PUT_LINE('USER_ID' || callCenterOrOps.ID);
END LOOP;
END;12)How to delete a COLUMN and ADD a COLUMN using Query in oracle
Answer :-
ALTER TABLE STUDENT DROP COLUMN NAME;--FOR DELETE [NAME] COLUMN FROM STUDENT TABLE.
ALTER TABLE STUDENT ADD NAME VARCHAR2(255);--FOR ADD [NAME] COLUMN FROM STUDENT TABLE.
13)How to create multiple CREATE and UPDATE query using ORACLE QUERY ?
Answer :-
NOTE:we didn't write logic here. :(
DECLARE
L_CNT PLS_INTEGER;
BEGIN
SELECT COUNT(0)
INTO L_CNT
FROM ALL_TABLES T
WHERE T.TABLE_NAME = 'SERVICE_REQUEST_TYPE';
IF L_CNT > 0 THEN
RETURN ;
END IF;
-- FOR CREATE A TABLE
EXECUTE IMMEDIATE '
CREATE TABLE SERVICE_REQUEST_TYPE
(ID NUMBER not null constraint SERVICE_REQUEST_TYPE_PK primary key,
REQUEST_NAME VARCHAR2(50),
REQUEST_CATEGORY NUMBER not null,
CODE NUMBER,
CREATED_AT TIMESTAMP(6) not null,
CREATED_BY NUMBER not null,
UPDATED_AT TIMESTAMP(6),
UPDATED_BY NUMBER)
';
--FOR INSERT DATA TO JUST CREATED TABLE
EXECUTE IMMEDIATE '
INSERT INTO SERVICE_REQUEST_TYPE(ID,REQUEST_NAME,REQUEST_CATEGORY,CODE,CREATED_AT,CREATED_BY, UPDATED_AT,UPDATED_BY)
VALUES (1,''HARDWATRE'',2,120,sysdate,300,null,null)
';
EXECUTE IMMEDIATE '
UPDATE SERVICE_REQUEST_TYPE SET REQUEST_NAME = ''SOFTWARE'' where REQUEST_NAME is not null
';
END;14)How to create ORACLE database sequence and use it in a java application?
Answer :-
CREATE SEQUENCE
create sequence SERVICE_REQUEST_TYPE_SEQ
order
nocache
/CREATE SEQUENCE generator
create trigger SERVICE_REQUEST_TYPE_SEQ_GEN
before insert
on SERVICE_REQUEST_TYPE
for each row
BEGIN
IF :NEW.ID = NULL OR :NEW.ID<0 THEN
SELECT SERVICE_REQUEST_TYPE_SEQ.NEXTVAL
INTO :NEW.ID
FROM DUAL;
END IF;
END;USE SQUENCE IN JAVA APPLICATION
15)How to get only date form current date and increment/decrement day using ORACLE query
Answer :-
SELECT TRUNC(SYSDATE-5) FROM DUAL;16)get 3rd high salary using ORACLE query
Answer :-
SELECT n.TOTAL_BBL_AMT FROM (SELECT TOTAL_BBL_AMT
FROM CORP_FILE_UPLOAD_INFO
order by TOTAL_BBL_AMT DESC) n offset 3 rows fetch next 1 rows only;17)get one to many table data using MS SQL query
Answer :-
SELECT
STRING_AGG(PN.phone,
',') as phoneNumber,--wil get result as comma separeted value like (01776767656,01531425247)
c.*
FROM
companies C
left join
phone_numbers PN
ON C.id = PN.companyid
group by
C.id,
C.created_at,
C.created_by,
C.deleted_at,
C.deleted_by,
C.is_active,
C.updated_at,
C.updated_by,
C.address,
C.email,
C.name,
C.tin; ##If we want to short the comma separated value the SQL will be
SELECT
STRING_AGG(PN.phone, ',') WITHIN GROUP (
ORDER BY
PN.phone DESC
) as phoneNumber,
c.*
FROM
companies C
left join phone_numbers PN ON C.id = PN.companyid
group by
C.id,
C.created_at,
C.created_by,
C.deleted_at,
C.deleted_by,
C.is_active,
C.updated_at,
C.updated_by,
C.address,
C.email,
C.name,
C.tin;
18)if given value is null then return all otherwise return based on the given input using ORACLE SQL query
Answer :-
SELECT * FROM USERS WHERE USERNAME= (
CASE WHEN :varname is null
THEN
USERNAME
ELSE
:varname
END
)19)get current time with sec.. and withour sec.. using ORACLE SQL query
Answer :-
SELECT TO_CHAR( SYSDATE, 'HH12:MI:SS AM' ) as currentTimeWithSec FROM DUAL;--12:22:23 PM
SELECT TO_CHAR( SYSDATE, 'HH12:MI AM' ) as currentTimeWithoutSec FROM DUAL;--12:20 PM20) get backup mysql db using command
Answer :-
mysqldump -h localhost --user=root --password=yourPass --result-file=D:\gehi\mysql_dump\iss_gp.sql --databases iss_gp
21) get backup oracle db using command
Answer :-
expdp DPDC/DPDC@orcl schemas=DPDC directory=DATA_PUMP_DIR dumpfile=DPDC_2020_11_17.dmp logfile=DPDC_2020_11_17.log
expdp uname/pass@orcl schemas=DPDC directory=DATA_PUMP_DIR dumpfile=DPDC_2020_11_17.dmp logfile=DPDC_2020_11_17.log
21) parse comma separeted String to string arrary and make a lopp on that array using PLSQL
Answer :-
DECLARE
input_string VARCHAR2(100) := 'kibria,anika,manik';
string_array DBMS_SQL.VARCHAR2_TABLE;
BEGIN
FOR i IN 1..REGEXP_COUNT(input_string, ',') + 1 LOOP
string_array(i) := REGEXP_SUBSTR(input_string, '[^,]+', 1, i);
END LOOP;
FOR i IN 1..string_array.COUNT LOOP
DBMS_OUTPUT.PUT_LINE(string_array(i));
END LOOP;
END;
22) get second high salary using java stream api
Answer :-
public static void main(String[] args) {
int[] salaries = {100, 200, 500, 50, 30};
int secondHighestSalary = Arrays.stream(salaries)
.distinct() // Remove duplicates if any
.sorted()//30,50,100,200,500
.skip(salaries.length - 2) // Skip all without last 2 item = [200,500]
.findFirst()//200
.orElseThrow(null); // Throw an exception if no element is found
System.out.println("Second highest salary: " + secondHighestSalary);//expected: 200
}
23) About hashCode() andequal()in depth with JDK code explanation
Answer :- click here.
24) About HashMap<>() Internal Architecture in depth with JDK code explanation
Answer :- click here.
25) About Fail Fast Vs Fail Safe Iterator In Java
Answer :- click here.
26) About Shallow Copy Vs. Deep Copy in Java
Answer :- click here.
27) Push data to queue using java with publishing guarantee
Answer :-
public void produceBatchesDataToQueue(List<String> tranIDs, Integer eventId, String actionPoint) throws IOException, TimeoutException {
for (int i = 0; i < tranIDs.size(); i++) {
LOGGER_I.info("Going to bind actual request data");
JBCollectionPolicyModelRequest request = buildAarongApiCallbackModel(tranIDs.get(i), actionPoint);
request.setEventId(eventId);
String message = gson.toJson(request);
LOGGER_I.info("Successfully bind data and prepare message :{}", message);
try {
LOGGER_I.info("Going to send rejected data to queue :{}",statusQueue);
//Now send data to queue
Channel publishChannel = ConnectionManager.getConnection(port, username, password, host).createChannel();
publishChannel.queueBind(statusQueue, exchangeName, batchRouting);
publishChannel.confirmSelect();
//crete messageId
long messageId = System.nanoTime();
// Create a CountDownLatch with a count of 1 to wait for acknowledgments
CountDownLatch latch = new CountDownLatch(1);
// Add a ConfirmListener for the channel
publishChannel.addConfirmListener(new ConfirmListener() {
@Override
public void handleAck(long deliveryTag, boolean multiple) throws IOException {
// This callback is called when a message is successfully delivered
System.out.println("Message published successfully with deliveryTag: " + deliveryTag);
// You can use your own logic here to correlate the deliveryTag with your messages.
latch.countDown(); // Release the latch
}
@Override
public void handleNack(long deliveryTag, boolean multiple) throws IOException {
// This callback is called when a message fails to be delivered
//TODO We can set alert from here for [Message delivery failed with deliveryTag].
LOGGER_I.info("Message delivery failed with deliveryTag: {} and messageId :{}" , deliveryTag,messageId);
// You can use your own logic here to correlate the deliveryTag with your messages.
latch.countDown(); // Release the latch
}
});
// Publish the message with the deliveryTag as a message property
AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()
.deliveryMode(2) // Persistent message to ensure if the server stops or crashes then after restart the server the message will still available
.messageId(String.valueOf(messageId))
.build();
publishChannel.basicPublish(exchangeName, batchRouting, properties, message.getBytes(StandardCharsets.UTF_8));
// Wait for the ConfirmListener callbacks or a specified timeout
/**
* We're waiting 500ms for the callback otherwise we treat this delivery as false.
* check the latch count is 0 or still 1 if 0 the condition will return true otherwise.
*/
if (latch.await(5000, TimeUnit.MILLISECONDS)) {
System.out.println("All messages were confirmed.");
} else {
//TODO we can set alert from here for [One or more messages failed to be confirmed within the timeout.]....
System.out.println("One or more messages failed to be confirmed within the timeout.");
}
// Close the channel after acknowledgments or timeout
publishChannel.close();
//LOGGER_I.info("Successfully send rejected data to queue :{}",statusQueue);
} catch (Exception e) {
//@TODO add alert during mq operation..
LOGGER_I.info("Queue Data Push time error :{}", e.getMessage(),e);
}
}
}28) Explain different type of isolation level in Java
Answer :-
29) Create Oracle PL/SQL trigger on table then update some column based on the triiger
Answer :-
create trigger SET_DEFAULT_PASSWORD
before update
on USERS
for each row
BEGIN
IF :NEW.PASSWORD IS NOT NULL AND :NEW.PASSWORD <> :OLD.PASSWORD THEN
:NEW.PASSWORD := '$2a$10$fYcxMH5SzN.DtrF.t3IpgeG4JcYuBPkUZA06dqvjVyI23MVa46h3i';
:NEW.NUMBER_OF_BAD_LOGIN:=0;
--Default Password: Abc@12345
END IF;
END;
/29) How to convert number to bangla taka as like 2323.34 = Two Thousand Three Hundred Twenty Three Taka Thirty Four Paisa Only
Answer :-
import java.text.DecimalFormat;
import java.util.Scanner;
public class NumberToBanglaTaka {
public static final String[] units = new String[]{"", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"};
public static final String[] tens = new String[]{"", "", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"};
public NumberToBanglaTaka() {
}
public static String convert(double n) {
DecimalFormat decimalFormat = new DecimalFormat("#0.00");
String numberAsString = decimalFormat.format(n);
String[] convert = numberAsString.split("\\.");
long taka = Long.parseLong(convert[0]);
int paisa = Integer.parseInt(convert[1]);
NumberToBanglaTaka numberToBanglaTaka = new NumberToBanglaTaka();
String totalTaka = "";
if (taka != 0L) {
totalTaka = numberToBanglaTaka.convertTaka(taka) + " Taka ";
}
if (taka == 0L && n < 0.0) {
totalTaka = "Minus ";
}
if (paisa > 0) {
totalTaka = totalTaka + numberToBanglaTaka.convertPaisa(paisa) + " Paisa ";
}
totalTaka = totalTaka + "Only";
return totalTaka;
}
public String convertTaka(Long n) {
if (n < 0L) {
return "Minus " + this.convertTaka(Math.abs(n));
} else {
int a;
if (n < 20L) {
a = Integer.parseInt(n.toString());
return units[a];
} else if (n < 100L) {
a = Integer.parseInt(n.toString());
return tens[a / 10] + (n % 10L != 0L ? " " : "") + units[a % 10];
} else if (n < 1000L) {
a = Integer.parseInt(n.toString());
return units[a / 100] + " Hundred" + (a % 100 != 0 ? " " : "") + this.convertTaka(n % 100L);
} else if (n < 100000L) {
return this.convertTaka(n / 1000L) + " Thousand" + (n % 10000L != 0L ? " " : "") + this.convertTaka(n % 1000L);
} else {
return n < 10000000L ? this.convertTaka(n / 100000L) + " Lakh" + (n % 100000L != 0L ? " " : "") + this.convertTaka(n % 100000L) : this.convertTaka(n / 10000000L) + " Crore" + (n % 10000000L != 0L ? " " : "") + this.convertTaka(n % 10000000L);
}
}
}
public String convertPaisa(int n) {
if (n < 20) {
return units[n];
} else {
return n < 100 ? tens[n / 10] + (n % 10 != 0 ? " " : "") + units[n % 10] : "";
}
}
public static void main(String[] args) {
while(true) {
Scanner scr = new Scanner(System.in);
double l = scr.nextDouble();
System.out.println(convert(l));
}
}
}30) Example for get flatten hierarchy from a self join table.
Answer :-
CREATE TABLE employee (
employee_id SERIAL PRIMARY KEY,
parent_id INT REFERENCES employee(employee_id) ON DELETE CASCADE,
name VARCHAR(255) NOT NULL,
department VARCHAR(100) NOT NULL,
UNIQUE (name)
);
insert into public.employee (employee_id, parent_id, name, department) values (1, null, 'kibria', 'java');
insert into public.employee (employee_id, parent_id, name, department) values (2, 1, 'avigit', 'php');
insert into public.employee (employee_id, parent_id, name, department) values (3, 2, 'adnan', 'c#');
insert into public.employee (employee_id, parent_id, name, department) values (4, 3, 'rakib', 'python');
insert into public.employee (employee_id, parent_id, name, department) values (5, 4, 'ahad', 'HR');
insert into public.employee (employee_id, parent_id, name, department) values (6, 5, 'Plabon', 'HR');
insert into public.employee (employee_id, parent_id, name, department) values (7, 6, 'saju', 'angular');
insert into public.employee (employee_id, parent_id, name, department) values (8, 4, 'William', 'c#');
select * from employee order by employee_id;
--Using this query we can get (Example for get flatten hierarchy from a self join table) by parent ID
WITH RECURSIVE EmployeeHierarchy AS (
SELECT employee_id, parent_id, name, department
FROM employee
WHERE :parentId is null and parent_id is null or parent_id = :parentId
UNION ALL
SELECT e.employee_id, e.parent_id, e.name, e.department
FROM employee e
INNER JOIN EmployeeHierarchy eh ON e.parent_id = eh.employee_id
)
SELECT *
FROM EmployeeHierarchy;OUTPUT:
ParentId : 4
31) Create binary tree using custom LinkedList and print preorder,inorder and postorder
Answer :-
32) Graph related DSA (BFS,DFS (With Internal structure diagram), minimum spanning tree(Prims and Kruskals))
Answer :-
33) RestTemplate for ignore SSL handshake and using proxy server
Answer :-
-
ignore SSL handshake and using proxy server.
@Bean("sslHandshakeIgnoreRestTemplate") public RestTemplate sslHandshakeIgnoreRestTemplate() { // Create a TrustManager that accepts all certificates TrustManager[] trustAllCertificates = new TrustManager[] { new X509TrustManager() { public X509Certificate[] getAcceptedIssuers() { return null; } public void checkClientTrusted(X509Certificate[] certs, String authType) {} public void checkServerTrusted(X509Certificate[] certs, String authType) {} } }; try { // Set up a SSL context that ignores all certificate validation SSLContext sslContext = SSLContext.getInstance("SSL"); sslContext.init(null, trustAllCertificates, new java.security.SecureRandom()); HttpsURLConnection.setDefaultSSLSocketFactory(sslContext.getSocketFactory()); // Set up a hostname verifier that accepts all hostnames HostnameVerifier allHostsValid = (hostname, session) -> true; HttpsURLConnection.setDefaultHostnameVerifier(allHostsValid); } catch (Exception e) { e.printStackTrace(); } // Create a RestTemplate with a SimpleClientHttpRequestFactory // This factory allows disabling SSL certificate validation RestTemplate restTemplate = new RestTemplate(clientHttpRequestFactory()); return restTemplate; }
-
ignore SSL handshake and using proxy server.
@Bean("sslHandshakeIgnoreRestTemplate") public RestTemplate sslHandshakeIgnoreRestTemplate() { // Create a TrustManager that accepts all certificates TrustManager[] trustAllCertificates = new TrustManager[] { new X509TrustManager() { public X509Certificate[] getAcceptedIssuers() { return null; } public void checkClientTrusted(X509Certificate[] certs, String authType) {} public void checkServerTrusted(X509Certificate[] certs, String authType) {} } }; try { // Set up a SSL context that ignores all certificate validation SSLContext sslContext = SSLContext.getInstance("SSL"); sslContext.init(null, trustAllCertificates, new java.security.SecureRandom()); HttpsURLConnection.setDefaultSSLSocketFactory(sslContext.getSocketFactory()); // Set up a hostname verifier that accepts all hostnames HostnameVerifier allHostsValid = (hostname, session) -> true; HttpsURLConnection.setDefaultHostnameVerifier(allHostsValid); } catch (Exception e) { e.printStackTrace(); } // Create a RestTemplate with a proxy server as gateway SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory(); Proxy proxy =new Proxy(Proxy.Type.HTTP,new InetSocketAddress("172.25.4.170",8080)); // This factory allows disabling SSL certificate validation requestFactory.setProxy(proxy); RestTemplate restTemplate = new RestTemplate(requestFactory); return restTemplate; } ```
34) Handle api call exceptions using RestTemplate
Answer :-
private BaseResponseBody<?> handleExceptions(Exception e) {
try {
if (e instanceof HttpServerErrorException) {
if (((HttpServerErrorException) e).getStatusCode() == HttpStatus.INTERNAL_SERVER_ERROR) {
String responseBody500 = ((HttpServerErrorException) e).getResponseBodyAsString();
logger.error("[NSU] Nsu server return INTERNAL SERVER ERROR and the response body is : {}", responseBody500);
return ResponseBuilder.getFailureResponse(HttpStatus.SERVICE_UNAVAILABLE,
"NSU System did not respond as per our expectation. " +
"You can try again or you can proceed to collect using 'North South University (Offline)' merchant.", e);
}
}
//if (e instanceof ResourceAccessException) {
Throwable cause = e.getCause();
if (cause instanceof ConnectException) {
//@INFO This usually means the server is unreachable. This could be due to the server being down, incorrect IP/hostname, or network issues.
return ResponseBuilder.getFailureResponse(HttpStatus.SERVICE_UNAVAILABLE,
"Unable to connect to the NSU System. Please check if the system is up and reachable " +
"or you can proceed to collect using 'North South University (Offline)' merchant.", e);
} else if (cause instanceof SocketTimeoutException) {
//@INFO This happens when the connection or read operation times out. You might need to increase your timeout settings or check the server's response times.
return ResponseBuilder.getFailureResponse(HttpStatus.SERVICE_UNAVAILABLE,
"NSU System did not respond within the anticipated time. " +
"Please contact with your administrator.", e);
} else if (cause instanceof UnknownHostException) {
//@INFO This indicates a DNS issue where the hostname cannot be resolved to an IP address.
return ResponseBuilder.getFailureResponse(HttpStatus.SERVICE_UNAVAILABLE,
"NSU System host could not be determined. " +
"You can proceed to collect using 'North South University (Offline)' merchant.", e);
} else if (cause instanceof NoRouteToHostException) {
//@INFO This means that the networking system is unable to find a route to the specified host, often due to network configuration issues.
return ResponseBuilder.getFailureResponse(HttpStatus.SERVICE_UNAVAILABLE,
"No route to the NSU System host." +
" You can proceed to collect using 'North South University (Offline)' merchant.", e);
} else if (cause instanceof PortUnreachableException) {
//specific exception in Java's networking API that occurs when an attempt to connect to a specific port on a remote host fails because the port is unreachable
return ResponseBuilder.getFailureResponse(HttpStatus.SERVICE_UNAVAILABLE,
"Defined port Unreachable." +
" You can proceed to collect using 'North South University (Offline)' merchant.", e);
} else if (cause instanceof ConnectionResetException) {
//that indicates a connection was forcibly closed by a peer. This exception often occurs when the server unexpectedly terminates the connection.
return ResponseBuilder.getFailureResponse(HttpStatus.SERVICE_UNAVAILABLE,
"Server unexpectedly terminates the connection." +
" Please contact with your administrator.", e);
} else if (cause instanceof IOException) {
//@INFO This is a broad exception for I/O issues, which could be due to stream interruptions, unexpected closures, or other input/output errors
return ResponseBuilder.getFailureResponse(HttpStatus.SERVICE_UNAVAILABLE,
"An I/O error occurred while trying to reach the NSU System. " +
"Please contact with your administrator.", e);
}
// }
return ResponseBuilder.getFailureResponse(HttpStatus.INTERNAL_SERVER_ERROR,
"[NSU] Something went wrong during call NSU API. Please contact with your administrator.", e);
} catch (Exception exception) {
logger.error("[NSU] Something went wrong during handle NSU api call exception :{}", exception.getMessage(), exception);
return ResponseBuilder.getFailureResponse(HttpStatus.INTERNAL_SERVER_ERROR,
"[NSU] Something went wrong during call NSU API. Please contact with your administrator.", exception);
}
}35) About Redis vs Db
Answer :-
https://gist.github.com/MdGolam-Kibria/594cd446444e9a23ef7e75927c0e9a2e
36) Log a transaction lifecycle
Answer :-
#For log full transaction life cycle
logging:
level:
org:
springframework:
orm:
jpa: DEBUGResult :
11/09/2024 02:48:35.295PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] INFO c.b.c.a.s.H2H.impl.H2HServiceImpl - xlsx File found to be parsed
11/09/2024 02:48:35.297PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] DEBUG o.s.orm.jpa.JpaTransactionManager - Found thread-bound EntityManager [SessionImpl(2015450469<open>)] for JPA transaction
11/09/2024 02:48:35.297PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] DEBUG o.s.orm.jpa.JpaTransactionManager - Creating new transaction with name [com.bbl.corpnet.api.service.H2H.H2HLegacyTransactionUploader.uploadBankExcel]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT
11/09/2024 02:48:35.299PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] DEBUG o.s.orm.jpa.JpaTransactionManager - Exposing JPA transaction as JDBC [org.springframework.orm.jpa.vendor.HibernateJpaDialect$HibernateConnectionHandle@13917d1f]
11/09/2024 02:48:35.301PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] INFO c.b.c.a.s.H.H2HLegacyTransactionUploader - Upload Bank Excel is called
11/09/2024 02:48:35.304PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] INFO c.b.c.a.s.H.H2HLegacyTransactionUploader - Reading XL file:/home/golamkibria/bracBank/corpnet-api/h2hFiles/CORPNET/11-09-2024/Third_Party_Transfer(1).xlsx
11/09/2024 02:48:35.779PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] INFO c.b.c.a.s.H.H2HLegacyTransactionUploader - Ready to call maker API for user:C3S_MAKER, companyId:4280
11/09/2024 02:48:35.779PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] DEBUG o.s.orm.jpa.JpaTransactionManager - Found thread-bound EntityManager [SessionImpl(2015450469<open>)] for JPA transaction
11/09/2024 02:48:35.779PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] DEBUG o.s.orm.jpa.JpaTransactionManager - Participating in existing transaction
11/09/2024 02:48:35.798PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] INFO c.b.c.a.m.s.i.UniversalTransactionMakerService - Maker API Request Payload
11/09/2024 02:48:37.186PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] DEBUG o.s.orm.jpa.JpaTransactionManager - Found thread-bound EntityManager [SessionImpl(2015450469<open>)] for JPA transaction
maker some operation inside the method going to another method.
11/09/2024 02:48:37.186PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] DEBUG o.s.orm.jpa.JpaTransactionManager - Participating in existing transaction
Hibernate: select common_trx_file_summary_seq.nextval from dual
11/09/2024 02:48:37.209PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] DEBUG o.s.orm.jpa.JpaTransactionManager - Found thread-bound EntityManager [SessionImpl(2015450469<open>)] for JPA transaction
11/09/2024 02:48:37.209PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] DEBUG o.s.orm.jpa.JpaTransactionManager - Participating in existing transaction
Hibernate: insert into corp_common_trx_file_summary (authorize_date, authorized_by, cancel_date, cancelled_by, charge_calculation_note, charge_status, client_batch_transaction_no, company_id, cr_account, dr_account, file_name, inserted_by, insert_date, is_charge_applicable, module_type, parent_transaction_reference, payment_by, payment_date, payment_type_id, rejected_by, reject_date, tran_remarks, is_scheduled, sig_limit_id, source_channel, status, total_amount, total_bbl, total_bbl_amt, total_eft, total_eft_amount, total_invalid_charge, total_invalid_charge_amount, total_rtgs, total_rtgs_amt, total_rejected_bbl, total_rejected_bbl_amt, total_rejected_eft, total_rejected_eft_amt, total_rejected_rtgs, total_rejected_rtgs_amt, total_trx, total_valid_amount, total_valid_charge, total_valid_charge_amount, total_valid_trx, uploaded_file_type, optimistic_lock_version, id) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
11/09/2024 02:48:37.301PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] WARN o.h.e.jdbc.spi.SqlExceptionHelper - SQL Error: 904, SQLState: 42000
11/09/2024 02:48:37.301PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] ERROR o.h.e.jdbc.spi.SqlExceptionHelper - ORA-00904: "SIGNATORY_ID": invalid identifier
11/09/2024 02:48:37.308PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] DEBUG o.s.orm.jpa.JpaTransactionManager - Participating transaction failed - marking existing transaction as rollback-only
11/09/2024 02:48:37.308PM 01001DF1F0CD4FA0A05A831F1B402F79 [http-nio-8442-exec-1] DEBUG o.s.orm.jpa.JpaTransactionManager - Setting JPA transaction on EntityManager [SessionImpl(2015450469<open>)] rollback-only
37) Local git set up guide with GitHub. using this way we can view the contributions summary to our GitHub account.
Answer :-
TO set up the GitHub with local git need to hit commad shared below,
1) set up the email address which is use in your GitHub email setting.
```
git config --global user.email "[email protected]"
```
2) check now to configuration successgully set or not using hit command below,
```
git config --global user.email
```
<b>Note:</b> the result should be same as the setup email.
38) Ubuntu useful commands
-
Remove a software
To remove a software (like FortiClient) from your system, use the command below:
sudo apt-get remove --purge forticlient -
Set all permissions in a directory
To give all users full read, write, and execute permissions on a directory, use the following command:
sudo chmod -R 777 /path/to/your/folder-R: This option applies the permissions recursively, meaning all files and subdirectories within the folder will also get these permissions. 777: This sets read (r), write (w), and execute (x) permissions for the owner, group, and others.
You can confirm the permissions by running the following command:
ls -l /path/to/your/folderThe output should look like:
drwxrwxrwx -
Run a command in the background (Ubuntu)
To run a command like openfortivpn in the background:
sudo openfortivpn ccc.brac.com:8098 -u golam.rabbaniIf you want to send this process to the background, follow these steps:
Press CTRL+Z to pause the process. Type bg to resume the process in the background. Use disown to detach the process from the terminal.You can verify if the service is running in the background using this command:
ps -ef | grep openfortivpn
39) Request Response logging including request served time using AOP example.
Answer :-
Click here : (https://gist.github.com/MdGolam-Kibria/d3a7023084f9fcaa0297ded37852c508)
40) HaProxy config example.
Answer :-
global
log /dev/log local0
# log 127.0.0.1:514 local0
chroot /var/lib/haproxy
stats timeout 30s
defaults
log global
mode http
option dontlognull
option httplog
timeout connect 500000
timeout client 5000000
timeout server 5000000
frontend mysite
bind :9014
http-request auth unless { http_auth(mycredentials) }
# route to a backend based on path's prefix
use_backend Report-mw if { path /report } || { path_beg /report/ }
use_backend Finacle-mw if { path /finacle } || { path_beg /finacle/ }
use_backend Bach-mw if { path /bach } || { path_beg /bach/ }
use_backend Corpapi-mw if { path /corpnet-api } || { path_beg /corpnet-api/ }
use_backend bmw if { path /billerMw } || { path_beg /billerMw/ }
use_backend app-vam if { path /api } || { path_beg /api/ }
use_backend trade-mw if { path /trade } || { path_beg /trade/ }
use_backend transaction-mw if { path /transaction-mw } || { path_beg /transaction-mw/ }
use_backend CorpCare-mw if { path /cc-mw } || { path_beg /cc-mw/ }
backend Report-mw
balance roundrobin
server server171 172.25.4.171:9005 check maxconn 30
server server92 172.25.5.92:9005 check maxconn 30
backend Finacle-mw
balance roundrobin
option forwardfor
option httpchk GET /finacle/health
server server171 172.25.4.171:9005 check maxconn 30
server server92 172.25.5.92:8062 check maxconn 30
backend transaction-mw
balance roundrobin
option forwardfor
option httpchk GET /transaction-mw/health
server server171 172.25.4.171:9005 check maxconn 30
server server92 172.25.5.92:9005 check maxconn 30
backend Bach-mw
balance roundrobin
option httpchk GET /bach/health
server server171 172.25.4.171:9005 check maxconn 30
server server92 172.25.5.92:9005 check maxconn 30
backend Corpapi-mw
balance roundrobin
option httpchk GET /corpnet-api/health
#http-request replace-path /corpnet-api(/)?(.*) /\2
server server171 172.25.4.171:9002 check maxconn 30
server server92 172.25.5.92:9002 check maxconn 30
backend bmw
balance roundrobin
option httpchk GET /billerMw/health
server server171 172.25.4.171:9005 check maxconn 30
server server92 172.25.5.92:9005 check maxconn 30
backend app-vam
balance roundrobin
option httpchk GET /api/health
server server171 172.25.4.171:9005 check maxconn 30
server server92 172.25.5.92:9005 check maxconn 30
backend dd-erapid-callback
balance roundrobin
option httpchk GET /api/health
server server171 172.25.4.171:9005 check maxconn 30
server server92 172.25.5.92:9005 check maxconn 30
backend trade-mw
balance roundrobin
option httpchk GET /trade/service/health
server server171 172.25.4.171:9005 check maxconn 30
server server92 172.25.5.92:9005 check maxconn 30
backend CorpCare-mw
balance roundrobin
option httpchk GET /cc-mw/
server server171 172.25.4.171:9005 check maxconn 30
server server92 172.25.5.92:9005 check maxconn 30
userlist mycredentials
user joe password $5$kuerVW/XiVT3rmDw$zhScxDJLtCaqWNAvaaP2aaXYPDU.NAFzJF3Iw077934
user alice password $5$1Hz6sm1AMf.bhg3F$HvyZ15rLE3VujvvhbgZAOO5ceL1p6iielHZfYtsrhI3
user mark password $5$fzFd5PQo3KLyZB2F$K7QdJ/AgzEK3V7eNIMbj.uwpUaYu17.thMALw5cBUR6
listen stats
bind *:9015
stats enable
stats refresh 10s
stats hide-version
stats show-node
stats uri /haproxy?stats
stats auth admin:adminspassword