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Articles on Trending Technologies
Technical articles with clear explanations and examples
Must we implement all the methods in a class that implements an interface in Java?
Yes, it is mandatory to implement all the methods in a class that implements an interface until and unless that class is declared as an abstract class.There are only two choices −Implement every method defined by the interface.Declare the class as an abstract class, as a result, forces you to subclass the class (and implement the missing methods) before you can create any objects.The only case the class do not need to implement all methods in the interface is when any class in its inheritance tree has already provided concrete (i.e. non-abstract) method implementations then the subclass is under no ...
Read MoreHow to move the horizontal slider right-to-left in Java?
At first, let us create a horizontal slider −JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 100, 55);Now, we will set it to move right-to-left using setInverted() −slider.setInverted(true);The following is an example to move the horizontal slider right-to-left −Examplepackage my; import java.awt.Color; import java.awt.Font; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JSlider; import javax.swing.WindowConstants; public class SwingDemo { public static void main(String[] args) { JFrame frame = new JFrame("Frame with Slider"); JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 100, 55); slider.setInverted(true); slider.setMinorTickSpacing(10); slider.setMajorTickSpacing(25); slider.setPaintTicks(true); ...
Read MoreMongoDB regex to display records whose first five letters are uppercase?
Let us first create a collection with documents −> db.upperCaseFiveLetterDemo.insertOne({"StudentFullName":"JOHN Smith"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7edef1a844af18acdffb2") } > db.upperCaseFiveLetterDemo.insertOne({"StudentFullName":"SAM Williams"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7ee011a844af18acdffb3") } > db.upperCaseFiveLetterDemo.insertOne({"StudentFullName":"CAROL Taylor"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7ee101a844af18acdffb4") } > db.upperCaseFiveLetterDemo.insertOne({"StudentFullName":"Bob Taylor"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7ee351a844af18acdffb5") } > db.upperCaseFiveLetterDemo.insertOne({"StudentFullName":"DAVID Miller"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7ee451a844af18acdffb6") }Following is the query to display all documents from a collection with the help of find() method −> db.upperCaseFiveLetterDemo.find().pretty();This will produce the following output −{ "_id" : ...
Read MoreWhat are Smart Contracts?
Cryptocurrency is entirely dependent on Block Chains to maintain their transactions. A block is like a page of a ledger book where some transactions are written in ink, permanent which cannot be altered. A block typically consists of transactions of bitcoin or any other cryptocurrency and the details of transactions - who has sent, who has received, timestamp and previous blocks information to link it to the Block chain. This information is passed through a hashing algorithm like SHA 256 and creates a 32-bit hash value. This hash value is irreversible.Thus a block is a permanent store of records, which ...
Read MoreFind and replace NumberLong type field in MongoDB?
Use $set operator along with update() for this. Let us first create a collection with documents. Here we have set one field as NumberLong −> db.findAndReplaceDemo.insertOne({"UserId":NumberLong(101)}); { "acknowledged" : true, "insertedId" : ObjectId("5cd2c960b64f4b851c3a13b6") } > db.findAndReplaceDemo.insertOne({"UserId":NumberLong(110)}); { "acknowledged" : true, "insertedId" : ObjectId("5cd2c966b64f4b851c3a13b7") } > db.findAndReplaceDemo.insertOne({"UserId":NumberLong(101)}); { "acknowledged" : true, "insertedId" : ObjectId("5cd2c969b64f4b851c3a13b8") } > db.findAndReplaceDemo.insertOne({"UserId":NumberLong(120)}); { "acknowledged" : true, "insertedId" : ObjectId("5cd2c96cb64f4b851c3a13b9") } > db.findAndReplaceDemo.insertOne({"UserId":NumberLong(130)}); { "acknowledged" : true, "insertedId" : ObjectId("5cd2c96eb64f4b851c3a13ba") }Following is the query to display all documents from a collection with the help of find() method ...
Read MoreHow to create a border with a raised beveled edge in Java?
Use the createRaisedBevelBorder() method to create a border with a raised beveled edge. We will set it on the label component −JLabel label; label = new JLabel("This has a border with a raised bevel edge!"); label.setBorder(BorderFactory.createRaisedBevelBorder());The following is an example to create a border with a raised beveled edge −Examplepackage my; import javax.swing.BorderFactory; import java.awt.Font; import javax.swing.JFrame; import javax.swing.JLabel; public class SwingDemo { public static void main(String[] args) throws Exception { JFrame frame = new JFrame("Demo"); JLabel label; label = new JLabel("This has a border with a raised bevel edge!"); ...
Read MoreMongoDB query to replace value in an array?
Use $set to replace value in an array. Let us first create a collection with documents −> db.replaceValueInArrayDemo.insertOne({"StudentScores":[45, 56, 78]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7f0421a844af18acdffb7") } > db.replaceValueInArrayDemo.insertOne({"StudentScores":[33, 90, 67]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7f0521a844af18acdffb8") }Following is the query to display all documents from a collection with the help of find() method −> db.replaceValueInArrayDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cd7f0421a844af18acdffb7"), "StudentScores" : [ 45, 56, 78 ] } { "_id" : ObjectId("5cd7f0521a844af18acdffb8"), "StudentScores" : [ ...
Read MoreWhat is Ethereum?
Before we talk about Ethereum let us first understand the concept of Decentralized network of Bitcoin which laid the foundation for the following Decentralized networks. Bitcoin digital currency was invented by Satoshi Nakamoto in 2009 as using a decentralized and transparent network.Bitcoin uses Cryptography + Proof of work + Decentralized network architecture together. The algorithm of Bitcoins is written in “Turing Incomplete” language, which understands only a limited set of orders like, who has sent the money, how much and who received it.While Bitcoin aims to remove a centralized authority to create the currency, Ethereum uses the Block Chain to ...
Read MoreHow to hide the track on the slider in Java?
To hide the track on the slider, you need to use the setPaintTrack() method and set it to FALSE −JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 100, 55); slider.setInverted(true); slider.setMinorTickSpacing(10); slider.setMajorTickSpacing(25); slider.setPaintTicks(true); slider.setPaintLabels(true); slider.setPaintTrack(false);The above method setPaintTrack() is by default set to TRUE.The following is an example to hide the track on the slider −Examplepackage my; import java.awt.Color; import java.awt.Font; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JSlider; import javax.swing.WindowConstants; public class SwingDemo { public static void main(String[] args) { JFrame frame = new JFrame("Frame with Slider"); JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 100, 55); ...
Read MoreAbsolute and Relative Imports in Python
Many times when we create python code we find that we need to access code from another python file or package. This is when you need to import that other python file or package into your current code. So the straight forward way to achieve this is just written the below statement at the top of your current python program.import package_name or module_name or from pacakge_name import module_name/object_nameWhen the above statement is parsed the interpreter does the following.The interpreter will look for names in the cache of all modules that have already been imported previously. The name of this cache ...
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