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Articles by Ankitha Reddy
Page 3 of 5
How to run Java package program
Let us look at an example that creates a package called animals. It is a good practice to use names of packages with lower case letters to avoid any conflicts with the names of classes and interfaces.Following package example contains interface named animals −/* File name : Animal.java */ package animals; interface Animal { public void eat(); public void travel(); }Now, let us implement the above interface in the same package animals −package animals; /* File name : MammalInt.java */ public class MammalInt implements Animal { public void eat() { System.out.println("Mammal eats"); } ...
Read MoreWhat is MySQL LOAD DATA statement?
LOAD DATAThis statement is used for importing the data from data files into our database. It reads data records directly from a file and inserts them into a table. Its syntax would be as follows −SyntaxLOAD DATA LOCAL INFILE '[path/][file_name]' INTO TABLE [table_name ];Here, a path is the address of the file.file_name is the name of the .txt filetable_name is the table where the data will be loaded.To illustrate the concept we are having the following data, separated by tab, in ‘A.txt’ whose path is d:/A.txt −100 John USA 10000 101 Paul UK 12000 102 Henry NZ 11000 103 Rick ...
Read MoreHow MySQL evaluates if I store date along with time value in a column having DATE data type?
As we know that the default format for MySQL DATE data type is “YYYY-MM-DD” and in this format, there is no possibility to store the time value. But still, if we store date along with time value in a column having DATE data type then MySQL will show a warning and store only the date value in that column. Following example will exhibit it −Examplemysql> Create table date_time_test(date DATE); Query OK, 0 rows affected (0.44 sec) mysql> Insert into date_time_test(date) values(‘2017-09-09 09:34:21’); Query OK, 1 row affected, 1 warning (0.03 sec) mysql> Select * from date_time_test; +------------+ | ...
Read MoreHow is it possible to store date such as February 30 in a MySQL date column?
Suppose we want to store the date such as February 30 in a MySQL table then we must have to first set ALLOW_INVALID_DATES mode enabled.For example, I am trying to add, without enabling ALLOW_INVALID_DATES mode, such kind of date in a table then MySQL will give an error as follows −mysql> Insert into date_testing(date) values('2017-02-30'); ERROR 1292 (22007): Incorrect date value: '2017-02-30' for column 'Date' at row1Now we need to enable ALLOW_INVALID_DATES mode enabled as follows −mysql> SET sql_mode = 'ALLOW_INVALID_DATES'; Query OK, 0 rows affected (0.00 sec) mysql> Insert into date_testing(date) values('2017-02-30'); Query OK, 1 row affected (0.14 ...
Read MoreWhat is runtime polymorphism or dynamic method overloading?
Polymorphism is the ability of an object to take on many forms. The most common use of polymorphism in OOP occurs when a parent class reference is used to refer to a child class object. Method overriding by a subclass is termed as runtime polymorphism. JVM determines the method to be executed at runtime instead of compile time. example class SuperClass { SuperClass get(){ System.out.println("SuperClass"); return this; } } public class Tester extends SuperClass { Tester get(){ System.out.println("SubClass"); return this; } public static void main(String[] args) { SuperClass tester = new Tester(); tester.get(); } } Output SubClass
Read MoreCamelCase in Java naming conventions
Java follows camel casing for objects, class, variables etc. If a name is having multiple words, the first letter is small then consecutive words are joint with the first letter as a capital case. Consider the following example − Taxation Department Class - TaxationDepartment Object - taxationDepartment Method - getTaxationDepartmentDetails Variable - taxationDepartment
Read MoreCreating multiple Java objects by one type only
You can create a List of object easily. Consider the following example, where I'll create an array of Employee objects and print their details in a for loop. import java.lang.reflect.InvocationTargetException; import java.util.ArrayList; import java.util.List; public class Tester implements Cloneable { private int data; public int getData() { return data; } public void setData(int data) { this.data = data; } public Tester(int data){ ...
Read MoreHow can we add a FOREIGN KEY constraint to the field of an existing MySQL table?
We can add a FOREIGN KEY constraint to a column of an existing MySQL table with the help of ALTER TABLE statement. Syntax ALTER TABLE table_name ADD FOREIGN KEY (colum_name) REFERENCES table having Primary Key(column_name); Example Suppose we want to add a FOREIGN KEY constraint on the table ‘Orders1’ referencing to the table ‘Customer’ which have column ‘Cust_Id’ as the Primary Key. It can be done with the help of the following query − mysql> Alter table orders1 add FOREIGN KEY(Cust_id) REFERENCES Customer(Cust_id); Query OK, 0 rows affected (0.21 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> ...
Read MoreHow can I fetch the value of REPLACE() function in the column name of our choice?
For fetching the values of REPLACE() function in our choice column name, we need to use the keyword ‘AS’ with REPLACE() function. Example mysql> Select Name, REPLACE(Name, 'G','S') AS Name_Changed from student Where Subject = 'Computers'; +--------+--------------+ | Name | Name_Changed | +--------+--------------+ | Gaurav | Saurav | | Gaurav | Saurav | +--------+--------------+ 2 rows in set (0.00 sec) The query above will give the result set of REPLACE() function in column name of our choice ‘Name_Changed’ which is given after keyword ‘AS’.
Read MoreHow MySQL behaves if I use INTERVAL keyword with an invalid date?
Actually, the behavior of MySQL depends upon the allow_invalid_dates mode. If this mode is enabled then MySQL will accept the invalid date and it would perform the date arithmetic as it performs with a valid date. Otherwise, if this mode is inactive then it will not accept the invalid date and would produce NULL as output. mysql> select '2017-02-30' + INTERVAL 7 day; +-------------------------------+ | '2017-02-30' + INTERVAL 7 day | +-------------------------------+ | NULL ...
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