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Articles on Trending Technologies
Technical articles with clear explanations and examples
High-level file operations in Python (shutil)
A number of functions for hgh level operations on files and directories have been defined in shutil module of Python’s standard library.copy()This function copies a file to a specified file in same or other directory. First parameter to the function is a string representation of existing file. Second argument is either name of resultant file or directory. If it is a directory, the file is coped in it with same name. The metadata of original file is not maintained.>>> import shutil >>> shutil.copy("hello.py", "newdir/") 'newdir/hello.py'copy2()This function is similar to copy() function except for the fact that it retains metadata of ...
Read MorePOJI in Java
POJI is an acronym for Plain Old Java Interface which corresponds to a Java standard interface which means that these interfaces are in the context of providing services in JEE. For example, OSGI service is offered through POJI in JEEIn other terms we can say that POJI is an ordinary interface without any specialty that is not inherited from any of the technology API specific interfaces or framework interfaces.Exampleinterface myCustomInterface { public void myMethod(); } interface mySecondCustomInterface extends myCustomInterface { public void mySecondMethod(); }Both interfaces would be called as POJI as they do not inherit any technology specific ...
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 MorePrimitive Wrapper Classes are Immutable in Java
In Java Immutable class is a class which once created and it's contents can not be changed.On same concept Immutable objects are the objects whose state can not be changed once constructed.Wrapper classes are made to be immutable due to following advantages −Since the state of the immutable objects can not be changed once they are created they are automatically synchronized.Immutable objects are automatically thread-safe, the overhead caused due to use of synchronisation is avoided.Once created the state of the wrapper class immutable object can not be changed so there is no possibility of them getting into an inconsistent state.The ...
Read MoreGet a list of Foreign Key constraints in MySQL
Let’s say we have a database “business” with number of tables. If you want to show only foreign key constraints, then use the following query −mysql> select * −> from information_schema.referential_constraints −> where constraint_schema = 'business';The following is the output displaying only foreign key constraints −+--------------------+-------------------+--------------------------+---------------------------+--------------------------+------------------------+--------------+-------------+-------------+-------------------+-----------------------+ | CONSTRAINT_CATALOG | CONSTRAINT_SCHEMA | CONSTRAINT_NAME | UNIQUE_CONSTRAINT_CATALOG | UNIQUE_CONSTRAINT_SCHEMA | UNIQUE_CONSTRAINT_NAME | MATCH_OPTION | UPDATE_RULE | DELETE_RULE | TABLE_NAME | REFERENCED_TABLE_NAME | +--------------------+-------------------+--------------------------+---------------------------+--------------------------+------------------------+--------------+-------------+-------------+-------------------+-----------------------+ | def | business | ConstChild ...
Read MoreInsert NULL value into INT column in MySQL?
You can insert NULL value into an int column with a condition i.e. the column must not have NOT NULL constraints. The syntax is as follows.INSERT INTO yourTableName(yourColumnName) values(NULL);To understand the above syntax, let us first create a table. The query to create a table is as follows.mysql> create table InsertNullDemo -> ( -> StudentId int, -> StudentName varchar(100), -> StudentAge int -> ); Query OK, 0 rows affected (0.53 sec)Here is the query to insert NULL whenever you do not pass any value for column. Here this column is StudentAge. MySQL inserts null value by default. The query to ...
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 MoreMySQL query to select records with a particular date?
You can use DATE() from MySQL to select records with a particular date. The syntax is as follows.SELECT *from yourTableName WHERE DATE(yourDateColumnName)=’anyDate’;To understand the above syntax, let us first create a table. The query to create a table is as follows.mysql> create table AllRecordsFromadate -> ( -> Id int, -> Name varchar(100), -> Age int, -> AdmissionDate datetime -> ); Query OK, 0 rows affected (0.53 sec)Insert some records in the table using insert command. The query to insert records is as follows.mysql> insert into AllRecordsFromadate values(101, 'John', 23, '2018-10-13'); Query OK, 1 row affected (0.18 sec) mysql> insert ...
Read MoreHow to add columns at specific position in existing table in MySQL?
To add columns at a specific position in existing table, use after command. The syntax is as follows −ALTER TABLE yourTableName ADD COLUMN yourColumnName data type AFTER yourExistingColumnName;To understand the above syntax, let us first create a table. The query to create a table is as follows.mysql> create table changeColumnPosition -> ( -> Id_Position1 int, -> Name_Position2 varchar(100), -> Address_Position4 varchar(200) -> ); Query OK, 0 rows affected (0.53 sec)Now you can check the description of existing table using desc command. The syntax is as follows −desc yourTableName;The following is the query to check the description.mysql> desc changeColumnPosition;The following is ...
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 ...
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