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Articles by Samual Sam
Page 7 of 151
Provider getVersion() method in Java
The version number of the provider can be obtained using the method getVersion() in the class java.security.Provider. This method requires no parameter and it returns the version number of the provider as required.A program that demonstrates this is given as follows −Exampleimport java.security.*; import java.util.*; public class Demo { public static void main(String[] argv) { try { KeyPairGenerator kpGenerator = KeyPairGenerator.getInstance("DSA"); Provider p = kpGenerator.getProvider(); System.out.println("The version number is: " + p.getVersion()); } catch (NoSuchAlgorithmException e) { ...
Read MoreJava Program to create String to super class type mapping
Here, we have a superclass Vehicle and within that some subclasses −class Vehicle { } class Motorcycle extends Vehicle { } class Bus extends Vehicle { } class Car extends Vehicle { }Now, we will create some strings for mapping with super class type −Mapmap = new HashMap(); map.put("motorcycle", new Motorcycle()); map.put("bus", new Bus()); map.put("car", new Car());Exampleimport java.util.HashMap; import java.util.Map; class Vehicle { } class Motorcycle extends Vehicle { } class Bus extends Vehicle { } class Car extends Vehicle { } public class Demo { public static void main(String... args) { Mapmap = new HashMap(); ...
Read MoreHow to keep the insertion order with Java LinkedHashMap?
To keep the insertion order with LinkedHashMap, use Iterator. Let us first create a HashMap and add elements to it −LinkedHashMaplHashMap = new LinkedHashMap(); lHashMap.put("1", "A"); lHashMap.put("2", "B"); lHashMap.put("3", "C"); lHashMap.put("4", "D"); lHashMap.put("5", "E"); lHashMap.put("6", "F"); lHashMap.put("7", "G"); lHashMap.put("8", "H"); lHashMap.put("9", "I");Now, get the values with the values() method. Iterate through the elements and display them −Collection collection = lHashMap.values(); Iterator i = collection.iterator(); while (i.hasNext()) { System.out.println(i.next()); }Exampleimport java.util.Collection; import java.util.Iterator; import java.util.LinkedHashMap; public class Demo { public static void main(String[] args) { LinkedHashMaplHashMap = new LinkedHashMap(); lHashMap.put("1", "A"); ...
Read MoreJava Program to read map by Map.Entry
To read the Map, first use getProperties() ad then iterator to iterate through the entire list of Map −Properties prop = System.getProperties(); Iterator i = prop.entrySet().iterator();Now, loop through Map.Entry and get the key-value pair for the Map −while (i.hasNext()) { Map.Entry entry = (Map.Entry) i.next(); System.out.println(entry.getKey() + " => " + entry.getValue()); }Exampleimport java.util.Iterator; import java.util.Map; import java.util.Properties; public class Demo { public static void main(String[] a) { Properties prop = System.getProperties(); Iterator i = prop.entrySet().iterator(); while (i.hasNext()) { Map.Entry entry = (Map.Entry) i.next(); ...
Read MoreJava Program to convert positive int to negative and negative to positive
To convert positive int to negative and vice-versa, use the Bitwise Complement Operator.Let us first initialize a positive int −int positiveVal = 200;Now, let us convert it to negative −int negativeVal = (~(positiveVal - 1));Now, let’s say we have the following negative int −int negativeVal = -300;The following will convert the negative to positive int −positiveVal = ~(negativeVal - 1);Examplepublic class Demo { public static void main(String[] args) throws java.lang.Exception { int positiveVal = 100; int negativeVal = (~(positiveVal - 1)); System.out.println("Result: Positive value converted to Negative = "+negativeVal); ...
Read MoreWriting files in background in Python
Here we are trying to do two tasks at a time, one in the foreground and the other in the background. We’ll write something in the file in the background and of a user input number, will find if it’s an odd or even number.Doing multiple tasks in one program in python is possible through multithreading inimport threading import time class AsyncWrite(threading.Thread): def __init__(self, text, out): threading.Thread.__init__(self) self.text = text self.out = out def run(self): f = open(self.out, "a") f.write(self.text + '') ...
Read MoreHow to track the order of insertion using Java collections?
To track the order of insertion, you can use Map.Entry() in case of a Map. Let’s say we have the following LinkedHashMap −Mapmap = new LinkedHashMap(); map.put("Jack", 0); map.put("Tim", 1); map.put("David", 2); map.put("Tom", 3); map.put("Kevin", 4); map.put("Jeff", 5);Now, loop through Map.Entry and get the order of insertion correctly with Key and Value −for (Map.Entryentry: map.entrySet()) { System.out.println(entry.getKey() + " => " + entry.getValue()); }Exampleimport java.util.LinkedHashMap; import java.util.Map; public class Demo { public static void main(String[] args) { Mapmap = new LinkedHashMap(); map.put("Jack", 0); map.put("Tim", 1); map.put("David", ...
Read MoreHow to use null value as key in Java HashMap
Yes, you can set null as key in Java HashMap. For this, let’s first create a HashMap with key and value pair −Mapmap = new HashMap(); map.put("Football", "A"); map.put("Squash", "B"); map.put("Cricket", "C"); map.put("Hockey", "D"); map.put("Rugby", "E");Now, let’s add null value as key −map.put(null, "H");You can try to get the value for key as “null” −map.get(null);Exampleimport java.util.HashMap; import java.util.Map; public class Demo { public static final void main(String[] args) { Mapmap = new HashMap(); map.put("Football", "A"); map.put("Squash", "B"); map.put("Cricket", "C"); map.put("Hockey", "D"); ...
Read MoreChecking if a HashSet contains certain value in Java
Let’s say the following is our Integer array −Integer arr[] = { 50, 100, 150, 200, 250, 300 };Set the above integer array in HashSet −Setset = new HashSet(Arrays.asList(arr));Now, let us check whether the HashSet contains certain value or not −set.contains(150)TRUE is returned if the value is in the List, else FALSE is the return value.Exampleimport java.util.Arrays; import java.util.HashSet; import java.util.Set; public class Demo { public static void main(String[] a) { Integer arr[] = { 50, 100, 150, 200, 250, 300 }; Setset = new HashSet(Arrays.asList(arr)); System.out.println(set.contains(200)); ...
Read MoreJava Program to fill an array with random numbers
Let us first crate an array −double[] arr = new double[5];Now, create Random class object −Random randNum = new Random();Now, fill the above array with random numbers −for (int i = 0; i < 5; i++) { arr[i] = randNum.nextInt(); }Exampleimport java.util.Arrays; import java.util.Random; public class Demo { public static void main(String args[]) { double[] arr = new double[5]; Random randNum = new Random(); for (int i = 0; i < 5; i++) { arr[i] = randNum.nextInt(); } System.out.println("Random numbers = "+Arrays.toString(arr)); } }OutputRandom numbers = [-6.59888981E8, 1.141160731E9, -9.931249E8, 1.335266582E9, 8.27918412E8]
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