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Java Articles
Page 26 of 450
Shadowing of static methods in Java\\n
When superclass and the subclass contain the same instance methods including parameters, when called, the superclass method is overridden by the method of the subclass.Exampleclass Super{ public void sample(){ System.out.println("Method of the Super class"); } } public class MethodOverriding extends Super { public void sample(){ System.out.println("Method of the Sub class"); } public static void main(String args[]){ MethodOverriding obj = new MethodOverriding(); obj.sample(); } }OutputMethod of the Sub classMethod shadowingWhen superclass and subclass contain the same method including parameters and if they are ...
Read MoreHow to import classes from within another directory/package in Java?
In Java classes and interfaces related to each other are grouped under a package. The package is nothing but a directory storing classes and interfaces of a particular concept. For example, all the classes and interfaces related to input and output operations are stored in the java.io package.There are two types of packages namely user-defined packages and built-in packages (pre-defined)The import keywordWhenever you need to use the classes from a particular package −First of all, you need to set a classpath for the JAR file holding the required package.Import the required class from the package using the import keyword. While ...
Read MoreHow to check if a file is readable, writable, or, executable in Java?
In general, whenever you create a file you can restrict/permit certain users from reading/writing/executing a file.In Java files (their abstract paths) are represented by the File class of the java.io package. This class provides various methods to perform various operations on files such as read, write, delete, rename, etc.In addition, this class also provides the following methods −setExecutble() − This method issued to set the execute permissions to the file represented by the current (File) object.setWritable() − This method is used to set the write permissions to the file represented by the current (File) object.setReadable() − This method is used ...
Read MoreAre Generics applied at compile time or run time?
Generics is a concept in Java where you can enable a class, interface and, method, accept all (reference) types as parameters. In other words it is the concept which enables the users to choose the reference type that a method, constructor of a class accepts, dynamically. By defining a class as generic you are making it type-safe i.e. it can act up on any datatype.Exampleclass Student{ T age; Student(T age){ this.age = age; } public void display() { System.out.println("Value of age: "+this.age); } } public class GenericsExample { ...
Read MoreCan we assign values to final arrays in Java?
The array is a container that can hold a fixed number of items and these items should be of the same type. Most of the data structures make use of arrays to implement their algorithms. The following are the important terms to understand the concept of Array.Element − Each item stored in an array is called an element.Index − Each location of an element in an array has a numerical index, which is used to identify the element.The size of the array will be determined at the time of creation.Examplepublic class ArrayExample { public static void main(String args[]){ ...
Read MoreCan you create an array of Generics type in Java?
Generics is a concept in Java where you can enable a class, interface and, method, accept all (reference) types as parameters. In other words it is the concept which enables the users to choose the reference type that a method, constructor of a class accepts, dynamically. By defining a class as generic you are making it type-safe i.e. it can act up on any datatype.Exampleclass Student{ T age; Student(T age){ this.age = age; } public void display() { System.out.println("Value of age: "+this.age); } } public class GenericsExample { ...
Read MoreTraversing contents of a hash map in Java
A map is a collection in Java which stores key-value pairs. The keys of this must not be null and each key should point to only one value. It is represented by the Map interface of java.util package. There are various classes which provide implementation to this interface.The HashMap is a class which implements the Map interface. It is based on the Hash table. It allows null values and null keys.In short, you can store key-value pairs in the HashMap object. Once you do so you can retrieve the values of the respective keys but, the values we use for ...
Read MoreAssigning arrays in Java.
While creating variables first of all we will declare them, initialize them, assign/re-assign values to them.Similarly, while creating arrays −You can declare an array just like a variable −int myArray[];You can create an array just like an object using the new keyword −myArray = new int[5];You can initialize the array by assigning values to all the elements one by one using the index −myArray [0] = 101; myArray [1] = 102;Assigning values to an arrayWhen we assign primitive values of one type to a variable of other (datatype) implicitly they are converted.But, when you try to assign a higher datatype ...
Read MoreWhat is need of introducing Generics, when Arrays already present in Java?
Arrays in Java are used to store homogeneous datatypes, where generics allow users to dynamically choose the type (class) that a method, constructor of a class accepts, dynamically.By defining a class generic you are making it type-safe i.e. it can act up on any datatype. To understand generics let us consider an example −Exampleclass Student{ T age; Student(T age){ this.age = age; } public void display() { System.out.println("Value of age: "+this.age); } } public class GenericsExample { public static void main(String args[]) { Student std1 ...
Read MoreCan we synchronize abstract methods in Java?
An abstract method is the one that does not have a body. It contains only a 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 (body) to it. If a class contains at least one abstract method, you must declare it abstract.Exampleimport java.io.IOException; abstract class MyClass { public abstract void display(); } public class AbstractClassExample extends MyClass{ public void display(){ System.out.println("subclass implementation of the display method"); } public static void main(String args[]) ...
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