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Articles on Trending Technologies
Technical articles with clear explanations and examples
How to prevent Reflection to break a Singleton Class Pattern?
A Singleton pattern states that a class can have a single instance and multiple instances are not permitted to be created. For this purpose, we make the constructor of the class a private and return a instance via a static method. But using reflection, we can still create multiple instance of a class by modifying the constructor scope. See the example below −Example - Breaking Singletonimport java.io.Serializable; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; public class Tester { public static void main(String[] args) throws InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException{ A a = A.getInstance(); ...
Read MoreOperator Functions in Python
In Python there are some additional standard library methods for mathematical operations, like arithmetic, logical, relational, bitwise etc. operations. These methods can be found under the operator module. To use it at first we need to import it the operator standard library module. import operator In this section we will see some operator functions for bitwise operations and container operations. Arithmetic Operations At first we will see the arithmetic operating functions. These are like below. Sr.No Functions & Description 1 add(x, y) The add() method is used to add two numbers x and y. ...
Read MoreJava Program to flip a bit in a BigInteger
To flip a bit in a BigInteger in Java, use the flipBit() method. This method returns a BigInteger whose value is equivalent to this BigInteger with the designated bit flipped.Exampleimport java.math.*; public class Demo { public static void main(String[] args) { BigInteger one, two; one = new BigInteger("7"); one = one.flipBit(3); System.out.println("Result: " +one); } }OutputResult: 15Let us see another example.Exampleimport java.math.*; public class Demo { public static void main(String[] args) { BigInteger bi1, bi2; bi1 = new BigInteger("8"); ...
Read MoreJava Program to shift bits in a BigInteger
To shift bits in a BigInteger, use the shiftLeft() or shiftRight() method.shiftLeft() methodThe java.math.BigInteger.shiftLeft(int n) returns a BigInteger whose value is (this > n). Sign extension is performed. The shift distance, n, may be negative, in which case this method performs a left shift. It computes floor(this / 2n).Exampleimport java.math.*; public class Demo { public static void main(String[] args) { BigInteger one; one = new BigInteger("25"); one = one.shiftRight(3); System.out.println("Result: " +one); } }OutputResult: 3
Read MoreGet the list of all the public methods in Java
A list of all the public methods of a class or interface that is represented by an object are provided using the method java.lang.Class.getMethods(). The public methods include that are declared by the class or interface and also those that are inherited by the class or interface.Also, the getMethods() method returns a zero length array if the class or interface has no public methods or if a primitive type, array class or void is represented in the Class object.A program that demonstrates this is given as follows −Exampleimport java.lang.reflect.Method; public class Main { public static void main(String[] argv) throws ...
Read MoreHow to prevent Serialization to break a Singleton Class Pattern?
A Singleton pattern states that a class can have a single instance and multiple instances are not permitted to be created. For this purpose, we make the constructor of the class a private and return a instance via a static method. But using serialization, we can still create multiple instance of a class. See the example below −Example - Breaking Singletonimport java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.io.Serializable; public class Tester{ public static void main(String[] args) throws ClassNotFoundException, IOException{ A a = A.getInstance(); A b = ...
Read MoreShift left in a BigInteger in Java
To shift left in a BigInteger, use the shiftLeft() method.The java.math.BigInteger.shiftLeft(int n) returns a BigInteger whose value is (this
Read MoreNarrowing Conversion in Java
Narrowing conversion is needed when you convert from a larger size type to a smaller size. This is for incompatible data types, wherein automatic conversions cannot be done.Let us see an example wherein we are converting long to integer using Narrowing Conversion.Examplepublic class Demo { public static void main(String[] args) { long longVal = 878; int intVal = (int) longVal; System.out.println("Long: "+longVal); System.out.println("Integer: "+intVal); } }OutputLong: 878 Integer: 878Let us see another example, wherein we are converting double to long using Narrowing Conversion.Examplepublic class Demo { public static void main(String[] args) { double doubleVal = 299.89; long longVal = (long)doubleVal; System.out.println("Double: "+doubleVal); ...
Read MoreDisplay the package name of a class in Java
The package for a class can be obtained using the java.lang.Class.getPackage() method with the help of the class loader of the class. If there is no package object created by the class loader of the class, then null is returned.A program that demonstrates this is given as follows −Exampleimport java.util.Date; public class Main { public static void main(String[] args) { Date d = new Date(); Package p = d.getClass().getPackage(); String pName = p.getName(); System.out.println("The package name is: " + pName); } }OutputThe package name is: java.utilNow ...
Read MoreHandling missing keys in Python dictionaries
In Python there is one container called the Dictionary. In the dictionaries, we can map keys to its value. Using dictionary the values can be accessed in constant time. But when the given keys are not present, it may occur some errors. In this section we will see how to handle these kind of errors. If we are trying to access missing keys, it may return errors like this. Example code country_dict = {'India' : 'IN', 'Australia' : 'AU', 'Brazil' : 'BR'} print(country_dict['Australia']) print(country_dict['Canada']) # This will return error Output AU --------------------------------------------------------------------------- KeyErrorTraceback (most recent call last) ...
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