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Articles by George John
Page 45 of 79
Remove all cancelled tasks from the timer's task queue in Java
One of the methods of the Timer class is the int purge() method. The purge() method removes all the canceled tasks from the timer’s task queue. Invoking this method does not affect the behavior of the timer, rather it eliminates references to the canceled tasks from the queue. The purge() method came into existence since JDK 1.5.The purge() method acts as a medium for space-time tradeoff where it trades time for space. More specifically, the time complexity of the method is proportional to n + c log n, where n is the number of tasks in the queue and c ...
Read MoreRead and write tar archive files using Python (tarfile)
The ‘tar’ utility was originally introduced for UNIX operating system. Its purpose is to collect multiple files in a single archive file often called tarball which makes it easy to distribute the files. Functions in tarfile module of Python’s standard library help in creating tar archives and extracting from the tarball as required. The archives can be constructed with gzip, bz2 and lzma compressions or without any compression at all.Main function defined in this module is main() using which writing to tar file or reading from it is accomplished.Open()This function returns a TarFile object corresponding to file name which is ...
Read MoreHexadecimal Number System
Hexadecimal Number System is one the type of Number Representation techniques, in which there value of base is 16. That means there are only 16 symbols or possible digit values, there are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F. Where A, B, C, D, E and F are single bit representations of decimal value 10, 11, 12, 13, 14 and 15 respectively. It requires only 4 bits to represent value of any digit. Hexadecimal numbers are indicated by the addition of either an 0x prefix or an h suffix.Position of every ...
Read MoreHow to display HTML in TextView in Android?
In Some situations, we should need to show HTML as text in android. Here is the simple solution to show HTML in TextView in android.Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.Step 2 − Add the following code to res/layout/activity_main.xml. Step 3 − Add the following code to src/MainActivity.javapackage com.example.andy.myapplication; import android.os.Bundle; import android.support.v4.text.HtmlCompat; import android.support.v7.app.AppCompatActivity; import android.widget.TextView; public class MainActivity extends AppCompatActivity { String htmlText = "What is Android?" + "Android is an open source and Linux-based ...
Read MoreHow to create a notification with NotificationCompat.Builder in Android?
Before getting into NotificationCompact.Builder, we should know what is a notification in android. Notification is just like as a message showing system on the action bar. just like missed call notification as shown belowThis example demonstrates how to integrate Android Notification.Step 1 − Create a new project in Android Studio, go to File ⇒ New Project, and fill all required details to create a new project.Step 2 − Add the following code to res/layout/activity_main.xml. Step 3 − Add the following code to src/MainActivity.javapackage com.example.andy.myapplication; import android.annotation.SuppressLint; import android.app.Notification; import android.app.NotificationChannel; import android.app.NotificationManager; import android.app.PendingIntent; import android.content.Context; import ...
Read MoreMoving a file from one directory to another using Java
We can use Files.move() API to move file from one directory to another. Following is the syntax of the move method.public static Path move(Path source, Path target, CopyOption... options) throws IOExceptionWheresource − Source path of file to be movedtarget − Target path of file to be movedoptions − options like REPLACE_EXISTING, ATOMIC_MOVEExampleimport java.io.IOException; import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; public class Tester { public static void main(String[] args) { //move file from D:/temp/test.txt to D:/temp1/test.txt //make sure that temp1 folder exists moveFile("D:/temp/test.txt", "D:/temp1/test.txt"); } private static void moveFile(String ...
Read MoreObject 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 ...
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