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Java Articles
Page 445 of 450
What is the difference between simple name, canonical name and class name in a Java class?
Canonical name of a Java class is the name of the class along with the package. For example, the canonical name of the class File is java.io.File. You can also get the canonical name of a particular class using Java method. The class named Class provides a method getCanonicalName(), this method returns canonical name of the current class. Example Live Demo import java.lang.*; public class ClassDemo { public static void main(String[] args) { ClassDemo c = new ClassDemo(); Class cls = c.getClass(); ...
Read MoreHow to declare, define and call a method in Java?
Following is the syntax to declare a method in Java. Syntax modifier return_type method_name(parameters_list){ //method body } Where, modifier − It defines the access type of the method and it is optional to use. return_type − Method may return a value. method_name − This is the method name. The method signature consists of the method name and the parameter list. parameters_list − The list of parameters, it is the type, order, and a number of parameters of a method. These are optional, method may contain zero parameters. method body − The method body defines ...
Read MoreWhat are static members of a Java class?
In Java, static members are those which belongs to the class and you can access these members without instantiating the class. The static keyword can be used with methods, fields, classes (inner/nested), blocks. Static Methods − You can create a static method by using the keyword static. Static methods can access only static fields, methods. To access static methods there is no need to instantiate the class, you can do it just using the class name as − Example Live Demo public class MyClass { public static void sample(){ ...
Read MoreAre the private variables and private methods of a parent class inherited by the child class in Java?
No, a child class can’t inherit private members of the parent class, it can inherit only protected, default, and public members of it. If you try it gives you a compile time error as: − Example class Super{ private int data = 30; public void display(){ System.out.println("Hello this is the method of the super class"); } } public class Sub extends Super{ public void greet(){ System.out.println("Hello this is the method of the sub class"); ...
Read MoreHow to convert Java Array/Collection to JSON array?
Google provides a library named org.json.JSONArray and, following is the maven dependency to add library to your project. com.googlecode.json-simple json-simple 1.1 The JSONArray class of the org.json package provides put() method. Using this method, you can populate the JSONArray object with the contents of the elements.Exampleimport org.json.JSONArray; public class ArrayToJson { public static void main(String args[]) { String [] myArray = {"JavaFX", "HBase", "JOGL", "WebGL"}; JSONArray jsArray = new JSONArray(); ...
Read MoreWhat is a method signature in Java?
The method signature consists of the method name and the parameter list. Example Live Demo public class MethodSignature { public int add(int a, int b){ int c = a+b; return c; } public static void main(String args[]){ MethodSignature obj = new MethodSignature(); int result = obj.add(56, 34); System.out.println(result); } } Output 90 Method ...
Read MoreCan a class in Java be both final and abstract?
An abstract cannot be instantiated. Therefore to use an abstract class you need to create another class and extend the abstract class and use it. If a class is final you can’t extend it further. So, you cannot declare a class both final and abstract. Example Still if you try to do so you will get a compile time error saying “illegal combination of modifiers:” final abstract class Demo{ public final void display(){ System.out.println("Hello welcome to tutorialspoint"); } } Output C:\Sample>javac Demo.java Demo.java:1: error: illegal ...
Read MoreCan constructors be marked final, abstract or static in Java?
Except public, protected and, private constructor does not allow any other modifier. When you use a final keyword with a method or constructor it cannot be overridden. But, a constructor in Java cannot be overridden therefore, there is no need of using the final keyword with the constructor. Since you cannot override a constructor you cannot provide body to it if it is made abstract. Therefore, you cannot use abstract keyword with the constructor. If you want to invoke a member of a class before instantiating the class you need to use static before it. But, contractors are called ...
Read MoreWhat is the class "class" in Java?
The Java.lang.Class class instance represent classes and interfaces in a running Java application. It has no public constructor. Example Following is the example demonstrates the usage of the class Class. The java.lang.Class.getCanonicalName() method returns the canonical name of the underlying class as defined by the Java Language Specification. It returns null if the class does not have a canonical name. Live Demo import java.lang.*; public class ClassDemo { public static void main(String[] args) { ClassDemo c = new ClassDemo(); Class cls = ...
Read MoreCan a constructor be overridden in java?
If super class and sub class have same methods including name, return type and parameters, and if you try to call it using the object of the sub class Then the method in the sub class is invoked. Constructor looks like method but it is not. It does not have a return type and its name is same as the class name. But, a constructor cannot be overridden. If you try to write a super class’s constructor in the sub class compiler treats it as a method and expects a return type and generates a compile time error. Example ...
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