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Programming Articles
Page 1501 of 2547
How to get the Checksum of a Byte Array in Java?
Create a Byte Array for which you want the Checksum −byte[] arr = "This is it!".getBytes();Now, create a Checksum object −Checksum checksum = new Adler32(); checksum.update(arr, 0, arr.length);The update() above updates the current checksum with the specified array of bytes.Now, get the checksum with getValue() method, which gives the current checksum value.Exampleimport java.util.zip.Adler32; import java.util.zip.Checksum; public class Demo { public static void main(String[] argv) throws Exception { byte[] arr = "This is it!".getBytes(); Checksum checksum = new Adler32(); checksum.update(arr, 0, arr.length); long res = checksum.getValue(); ...
Read MoreCan we cast an object reference to an interface reference in java? If so when?
Yes, you can.If you implement an interface and provide body to its methods from a class. You can hold object of the that class using the reference variable of the interface i.e. cast an object reference to an interface reference.But, using this you can access the methods of the interface only, if you try to access the methods of the class a compile time error is generated.ExampleIn the following Java example, we have an interface named MyInterface with an abstract method display().We have a class with name InterfaceExample with a method (show()). In addition to it, we are implementing the ...
Read MoreJava Program to change a file attribute to writable
Let’s say our file is “input.txt”, which is set read-only −File myFile = new File("input.txt"); myFile.createNewFile(); myFile.setReadOnly();Now, set the above file to writable −myFile.setWritable(true);After that, you can use canWrite() to check whether the file is writable or not.Exampleimport java.io.File; public class Demo { public static void main(String[] args) throws Exception { File myFile = new File("input.txt"); myFile.createNewFile(); myFile.setReadOnly(); if (myFile.canWrite()) { System.out.println("Writable!"); } else { System.out.println("Read only mode!"); } // ...
Read MoreCan a method local inner class access the local final variables in Java?
Yes, we can access the local final variables using the method local inner class because the final variables are stored on the heap and live as long as the method local inner class object may live.Method Local Inner ClassA local inner class instance can be delivered as an argument and retrieved from the methods and it is available inside a valid scope.The only limitation in method local inner class is that a local parameter can be executed only when it is defined as final.The method executing the local parameters can be called after the execution of the method, within which the local inner ...
Read MoreExplain restrictions on using enum in java?
Enumeration (enum) in Java is a datatype which stores a set of constant values. You can use enumerations to store fixed values such as days in a week, months in a year etc.You can define an enumeration using the keyword enum followed by the name of the enumeration as −enum Days { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY }Points to keep in mindYou need to keep the following points in mind while declaring an enum −It is recommended to write the name of the constants in all capital letters as −public class EnumerationExample { enum Days { ...
Read MoreCharBuffer put() method in Java
The required value can be written at the current position of the buffer and then the current position is incremented using the method put() in the class java.nio.CharBuffer. This method requires a single parameter i.e. the value to be written in the buffer and it returns the buffer in which the value is inserted.A program that demonstrates this is given as follows −Exampleimport java.nio.*; import java.util.*; public class Demo { public static void main(String[] args) { int n = 5; try { CharBuffer buffer = CharBuffer.allocate(5); ...
Read MoreThe toArray(T[] a) method of CopyOnWriteArrayList in Java
The difference between toArray() and toArray(T[] arr) of the CopyOnWriteArrayList class is that both the methods returns an array containing all of the elements in this collection, but the latter has some additional features i.e. the runtime type of the returned array is that of the specified array.The syntax is as followspublic T[] toArray(T[] arr)Here, the parameter arr is the array into which the elements of the list are to be stored.To work with CopyOnWriteArrayList class, you need to import the following packageimport java.util.concurrent.CopyOnWriteArrayList;The following is an example to implement CopyOnWriteArrayList class toArray() method in JavaExampleimport java.util.Arrays; import java.util.concurrent.CopyOnWriteArrayList; ...
Read MoreCan we declare an abstract method, private, protected, public or default in java?
A method which does not have body is known as abstract method. It contains only method signature with a semi colon and, an abstract keyword before it.public abstract myMethod();To use an abstract method, you need to inherit it by extending its class and provide implementation to it.Declaring an abstract method privateIf a method of a class is private, you cannot access it outside the current class, not even from the child classes of it.But, incase of an abstract method, you cannot use it from the same class, you need to override it from subclass and use.Therefore, the abstract method cannot ...
Read MoreComparison of Exception Handling in C++ and Java
The exception handling feature is present almost any object oriented languages nowadays. In C++ and Java also we can get this kind of feature. There are some similarities between exception handling in C++ and exception handling in Java, like in both languages we have to use the try-catch block. Though there are some difficulties also. These are like below −In C++, we can throw any type of data as exception. Any type of data means primitive datatypes and pointers also. In Java we can only throw the throwable objects. Subclasses of any throwable class will also be throwable.Example#include using ...
Read MoreThe indexOf() method of CopyOnWriteArrayList class in Java
The indexOf() method of the CopyOnWriteArrayList class is used to get the index of the first occurrence of an element. The method has two two forms. Let us see them one by oneindexOf(Object o) methodThe indexOf(Object o) is used to get the index of the first occurrence of an element.The syntax is as followsindexOf(Object o)Here, o is the element for which you want the index. To work with CopyOnWriteArrayList class, you need to import the following packageimport java.util.concurrent.CopyOnWriteArrayList;The following is an example to implement CopyOnWriteArrayList class indexOf() method in JavaExampleimport java.util.concurrent.CopyOnWriteArrayList; public class Demo { public static void main(String[] ...
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