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A JSONObject is an unordered collection of a key, value pairs, and the values can be any of these types like Boolean, JSONArray, JSONObject, Number and String. The constructor of a JSONObject can be used to convert an external form JSON text into an internal form whose values can be retrieved with the get() and opt() methods or to convert values into a JSON text using the put() and toString() methods.In the below example, we can sort the values of a JSONObject in the descending order.Exampleimport org.json.*; import java.util.*; public class JSonObjectSortingTest { public static void main(String[] args) { ... Read More
In Java methods, parameters accept arguments with three dots. These are known as variable arguments.sample(int args …){}If they are used you can pass a different number of arguments each time you call these methods.Examplepublic class Sample { void demoMethod(String... args) { for (String arg: args) { System.out.println(arg); } } public static void main(String args[] ) { new Sample().demoMethod("ram", "rahim", "robert"); new Sample().demoMethod("krishna", "kasyap") } }Outputram rahim robert krishna kasyap
You can access the private methods of a class using java reflection package.Step1 − Instantiate the Method class of the java.lang.reflect package by passing the method name of the method which is declared private.Step2 − Set the method accessible by passing value true to the setAccessible() method.Step3 − Finally, invoke the method using the invoke() method.Exampleimport java.lang.reflect.Method; public class DemoTest { private void sampleMethod() { System.out.println("hello"); } } public class SampleTest { public static void main(String args[]) throws Exception { Class c = Class.forName("DemoTest"); Object obj = c.newInstance(); ... Read More
You can create an object of the class named Class in two ways −Using new keyword as −Class obj = new Class();Using the forName() method of the class named Class.Class obj = Class.forName("DemoTest");
Typecasting is converting one data type to another.Up-casting − Converting a subclass type to a superclass type is known as up casting.Exampleclass Super { void Sample() { System.out.println("method of super class"); } } public class Sub extends Super { void Sample() { System.out.println("method of sub class"); } public static void main(String args[]) { Super obj =(Super) new Sub(); obj.Sample(); } }Down-casting − Converting a superclass type to a subclass type is known as downcasting.Exampleclass Super { void Sample() { ... Read More
Recursion is where which a method class itself.Examplepublic class RecursionExample { private static long factorial(int n) { if (n == 1) return 1; else return n * factorial(n-1); } public static void main(String args[]) { RecursionExample obj = new RecursionExample(); long result = obj.factorial(5); System.out.println(result); } }
You can access the private methods of a class using java reflection package.Step1 − Instantiate the Method class of the java.lang.reflect package by passing the method name of the method which is declared private.Step2 − Set the method accessible by passing value true to the setAccessible() method.Step3 − Finally, invoke the method using the invoke() method.Exampleimport java.lang.reflect.Method; public class DemoTest { private void sampleMethod() { System.out.println("hello"); } } public class SampleTest { public static void main(String args[]) throws Exception { Class c = Class.forName("DemoTest"); Object obj ... Read More
PostgreSql database is by default installed on port number 5432. Python interface to PostgreSql is provided by installing psycopg2 module. Assuming that test database and employee table with fname, sname, age, gender and salary fields is available.First establish connection and obtain cursor object by following statements in Python script.import psycopg2 conn = psycopg2.connect(database = "test", user = "postgres", password = "pass123", host = "localhost", port = "5432") cur = conn.cursor()Data to be inserted in employee table is stored in the form of tuple objectt1=('Mac', 'Mohan', 20, 'M', 2000)Next set up the insert query using this tuplesql="insert into employee values(%s, %s, ... Read More
Assuming that MySQL database named as test is present on server and a table named employee is also created. The table has five fields fname, lname, age, gender, and salary.A tuple object containing data of a record is defined ast1=('Mac', 'Mohan', 20, 'M', 2000)To establish interface between MySQL and Python 3, you need to install PyMySQL module. Then you can set up the connection using following statementsimport PyMySQL # Open database connection db = PyMySQL.connect("localhost", "root", "", "test" ) # prepare a cursor object using cursor() method cursor = db.cursor()Next step is to set up the insert query using data ... Read More
Download the latest version of Java from the official site. Run the .exe to install Java on your machine. Once you installed Java on your machine, you will need to set environment variables to point to correct installation directories −Setting Up the Path for Windows:Assuming you have installed Java in c:\Program Files\java\jdk directory − Right-click on 'My Computer' and select 'Properties'.Click the 'Environment variables' button under the 'Advanced' tab.Now, alter the 'Path' variable so that it also contains the path to the Java executable. Example, if the path is currently set to 'C:\WINDOWS\SYSTEM32', then change your path to read 'C:\WINDOWS\SYSTEM32;c:\Program Files\java\jdk\bin'.Read More