Article Categories
- All Categories
-
Data Structure
-
Networking
-
RDBMS
-
Operating System
-
Java
-
MS Excel
-
iOS
-
HTML
-
CSS
-
Android
-
Python
-
C Programming
-
C++
-
C#
-
MongoDB
-
MySQL
-
Javascript
-
PHP
Articles by George John
Page 31 of 79
Object Serialization with inheritance in Java
In Serialization when inheritance is introduced then on the basis of superclass and subclass certain cases have been defined which make the understanding of Serialization in each case much simpler. The fundamental rules which should be followed are as below.1. When super class is implements Serializable interface and subclass is not.In this case the object of subclass get serialized by default when superclass get serialize, even if subclass doesn't implements Serializable interface.Examplepublic class TestSerialization { public static void main(String[] args) throws IOException, ClassNotFoundException { B obj = new B(); FileOutputStream fos = new ...
Read MorePOJO vs Java Beans
As we know that in Java POJO refers to the Plain old Java object.POJO and Bean class in Java shares some common features which are as follows −Both classes must be public i.e accessible to all.Properties or variables defined in both classes must be private i.e. can't be accessed directly.Both classes must have default constructor i.e no argument constructor.Public Getter and Setter must be present in both the classes in order to access the variables/properties.The only difference between both the classes is Java make java beans objects serialized so that the state of a bean class could be preserved in ...
Read MoreMySQL sort string number?
To sort string number, use the CAST() function from MySQL. The syntax is as follows −SELECT *FROM yourTableName ORDER BY (yourColumnName as Decimal(integerValue, integerValueAfterDecimalPoint)) desc;To understand the above syntax, let us first create a table. The query to create a table is as follows −mysql> create table SortingStringDemo -> ( -> Amount varchar(10) -> ); Query OK, 0 rows affected (0.91 sec)Insert some records in the table using insert command. The query is as follows.mysql> insert into SortingStringDemo values('12.34'); Query OK, 1 row affected (0.21 sec) mysql> insert into SortingStringDemo values('124.50'); Query OK, 1 row affected (0.56 sec) ...
Read MoreFile and Directory Comparisons in Python
Python’s standard library has filecmp module that defines functions for comparison of files and directories. This comparison takes into consideration the properties of files in addition to data in them.Example codes in this article use following file and directory structure.Two directories dir1 and dir2 are first created under current working directory. They contain following files.--dir1/newfile.txt-- This is a file in dir1 --dir1/file1.txt-- Hello Python --dir1/file2.txt-- Python Standard Library --dir2/file1.txt-- Hello Python --dir2/file2.txt-- Python LibraryLet us now describe various comparison functions in filecmp module.filecmp.cmp(f1, f2, shallow=True)This function compares the two files and returns True if they are identical, False otherwise. The ...
Read MoreChange the Auto Increment counter in MySQL?
In MySQL, auto increment counter starts from 0 by default, but if you want the auto increment to start from another number, use the below syntax.ALTER TABLE yourTable auto_increment=yourIntegerNumber;To understand the above syntax, let us first create a table. The query to create a table is as follows.mysql> create table startAutoIncrement -> ( -> Counter int auto_increment , -> primary key(Counter) -> ); Query OK, 0 rows affected (0.90 sec)Implement the above syntax to begin auto increment from 20. The query is as follows.mysql> alter table startAutoIncrement auto_increment=20; Query OK, 0 rows affected (0.30 sec) Records: 0 Duplicates: 0 Warnings: ...
Read MoreIs there any whoami function or command in MySQL like UNIX?
There is no whoami function in MySQL. The whoami can be used to know the current user in UNIX. Use user() or current_user() function from MySQL for the same purpose.The following is the output.+-----------+ | version() | +-----------+ | 8.0.12 | +-----------+ 1 row in set (0.00 sec)Case 1 −Using CURRENT_USER() function.The query to know the current user is as follows.mysql> select current_user();The following is the output.+----------------+ | current_user() | +----------------+ | root@% | +----------------+ 1 row in set (0.00 sec)Case 2 − Using USER() function.The query is as follows −mysql> select user();The following is ...
Read MoreLegendre’s Formula in java\\n
You can calculate the exponent of the largest power of a PrimeNumber that divides the factorial n! using Legendre's formula.Programimport java.util.Scanner; public class LegendresFormula { static int Largestpower(int n, int p) { int ans = 0; while (n > 0) { n /= p; ans += n; } return ans; } public static void main (String[] args) { Scanner sc = new Scanner(System.in); System.out.println("Enter the n value :"); ...
Read Morek-th prime factor of a given number in java
Following is the Java program which prints the kth prime factor of a number n, when k and n are given.Programimport java.util.Scanner; public class KthPrimeFactor { public static void main(String args[]) { int number, k, factor = 0; Scanner sc = new Scanner(System.in); System.out.println("Enter a number :"); number = sc.nextInt(); System.out.println("Enter the k value :"); k = sc.nextInt(); int temp = k-1; for(int i = 2; i< number; ...
Read MoreWhen running UPDATE … datetime = NOW(); will all rows updated have the same date/ time in mysql?
The now() function returns the constant time that exhibits the time at which any statement began to execute. The sysdate() function returns the exact same datetime at which it executed the statement from MySQL 5.0.13.Suppose if you are updating datetime with now() in triggers or stored procedure, the now() method returns the time at which time the triggering and stored procedure begin to execute.Here is the demo of update with now(). Let us first create a table. The query to create a table is as follows −mysql> create table NowDemo -> ( -> DueDateTime datetime -> ); Query OK, 0 ...
Read MoreGet the index of last substring in a given string in MySQL?
To get the index of last substring in a given string, use the char_length() function. First, we need to calculate string length and subtract the last sub string length from the entire length. The difference in length is index of substring.SyntaxThe syntax is as follows −select CHAR_LENGTH(yourColumnName) - LOCATE('yourDelimiter ', REVERSE(yourColumnName))+1 as anyVariableName from yourTableName;To understand the above syntax, let us first create a table. The query to create a table is as follows −mysql> create table SubStringIndexDemo -> ( -> Words varchar(200) -> ); Query OK, 0 rows affected (0.57 sec)Insert some records in the table ...
Read More