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Here we will see what are the differences between destructor and the free() functions in C++. The destructor is used to perform some action, just before the object is destroyed. This action may not freeing up the memory, but can do some simple action such as displaying one message on screen.The free() function is used in C, in C++, we can do the same thing using delete keyword also. When the object is deleted using free() or delete, the destructor is invoked. The destructor function takes no argument and returns nothing. This function is called when free or delete is ... Read More
You can get the name of a particular column using the getColumnName() method of the ResultSetMetadata interface.This method accepts an integer value representing the index of a column and returns a String value representing the name of the specified column.Let us create a table with name MyPlayers in MySQL database using CREATE statement as shown below −CREATE TABLE MyPlayers( ID INT, First_Name VARCHAR(255), Last_Name VARCHAR(255), Date_Of_Birth date, Place_Of_Birth VARCHAR(255), Country VARCHAR(255), PRIMARY KEY (ID) );Now, we will insert 7 records in MyPlayers table using INSERT statements −insert into MyPlayers values(1, 'Shikhar', 'Dhawan', DATE('1981-12-05'), 'Delhi', 'India'); insert into MyPlayers ... Read More
We can find the minimum value of an array using Math.min() and sort()1) Math.min() Math.min() function usually takes all the elements in an array and scrutinize each and every value to get the minimum value.It's methodology is discussed in the below example. Live DemoExample function minimum(value) { if (toString.call(value) !== "[object Array]") return false; return Math.min.apply(null, value); } document.write(minimum([6, 39, 55, 1, 44])); Output12) sort()Using sort() and compare functions we can write the elements in ascending or descending order, later on using length property we can ... Read More
We can set or disallow selection of row in the table using setRowSelectionAllowed().Let’s say the following is our table −DefaultTableModel tableModel = new DefaultTableModel(); JTable table = new JTable(tableModel);If you want to allow selection of row, then set the method to TRUE −table.setRowSelectionAllowed(true);If you want to disallow selection of row, then set the method to FALSE −table.setRowSelectionAllowed(false);We have disallowed selection of rows in the below example −Examplepackage my; import javax.swing.JFrame; import javax.swing.JScrollPane; import javax.swing.JTable; import javax.swing.table.DefaultTableModel; public class SwingDemo { public static void main(String[] argv) throws Exception { DefaultTableModel tableModel = new DefaultTableModel(); ... Read More
Differences between Map and WeakMapThe functional mechanism of Map and WeakMap is same but they have little differences.1) A WeakMap accepts only objects as keys whereas a Map, in addition to objects, accepts primitive datatype such as strings, numbers etc.2) WeakMap objects doesn't avert garbage collection if there are no references to the object which is acting like a key. Therefore there is no method to retrieve keys in WeakMap, whereas in Map there are methods such as Map.prototype.keys() to get the keys.3) There is no size property exists in WeakMap.MapIt is used to associate a key to a value ... Read More
Use the $push operator to add a sub-document. Let us first create a collection with documents −> db.subDocumentToSubDocumentDemo.insertOne( { "_id" :101, "StudentName" : "Larry", "StudentAge" : 21, "StudentDetails" : [ { "StudentCountryName" : "US", "StudentFavouriteSubjectList" : [ ] } ] } ); { "acknowledged" : true, "insertedId" : 101 }Following is the query to display all documents from a collection with the help ... Read More
A Json array is an ordered collection of values that are enclosed in square brackets i.e. it begins with ‘[’ and ends with ‘]’. The values in the arrays are separated by ‘, ’ (comma).Sample JSON array{ "books": [ Java, JavaFX, Hbase, Cassandra, WebGL, JOGL] }The json-simple is a light weight library which is used to process JSON objects. Using this you can read or, write the contents of a JSON document using Java program.JSON-Simple maven dependencyFollowing is the maven dependency for the JSON-simple library − com.googlecode.json-simple json-simple ... Read More
The HTML DOM select add() method adds a new option to a drop-down list in an HTML document.SyntaxFollowing is the syntax −object.add(option, index)ExampleLet us see an example of HTML DOM select add() method − Live Demo html{ height:100%; } body{ text-align:center; color:#fff; background: radial-gradient( circle farthest-corner at 23.1% 64.6%, rgba(129, 125, 254, 1) 0%, rgba(111, 167, 254, 1) 90% ) no-repeat; height:100%; } p{ font-weight:700; font-size:1.1rem; } .drop-down{ ... Read More
Python functions can return multiple values. These values can be stored in variables directly. A function is not restricted to return a variable, it can return zero, one, two or more values.This is the default property of python to return multiple values/variables which is not available in many other programming languages like C++ or Java.For returning multiple values from a function, we can return tuple, list or dictionary object as per our requirement.Method 1: Using tupledef func(x): y0 = x+ 1 y1 = x * 3 y2 = y0 ** 3 return (y0, y1, y2)However, above ... Read More
The getColumnName() method of the ResultSetMetaData (interface) retrieves and returns the name of the specified column in the current ResultSet object.This method accepts an integer value representing the index of a column and, returns a String value representing the name of the specified column.To get the ResultSetMetaData object, you need to −Register the Driver: Select the required database register the Driver class of the particular database using the registerDriver() method of the DriverManager class or, the forName() method of the class named Class.DriverManager.registerDriver(new com.mysql.jdbc.Driver());Get connection: Create a connection object by passing the URL of the database, username and password of a ... Read More