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Programming Articles
Page 2547 of 2547
Are 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 MoreWhat are reference data types in Java?
Reference datatypes in java are those which contains reference/address of dynamically created objects. These are not predefined like primitive data types. Following are the reference types in Java. class types − This reference type points to an object of a class. array types − This reference type points to an array. interface types − This reference type points to an object of a class which implements an interface. Once we create a variable of these types (i.e. when we create an array or object, class or interface). These variables only store the address of these values. Default ...
Read MoreWhat is the difference between Java references and pointers in other languages?
Reference datatypes in java are those which contains reference/address of dynamically created objects. These are not predefined like primitive data types. Following are the reference types in Java. class types − This reference type points to an object of a class. array types − This reference type points to an array. interface types − This reference type points to an object of a class which implements an interface. Once we create a variable of these types (i.e. when we create an array or object, class or interface). These variables only store the address of these values. Default ...
Read MoreWhy are classes sometimes declared final in Java?
If a class is declared final, you cannot inherit it. If you try it gives you a compile-time error as − Example final class Super { private int data = 30; } public class Sub extends Sub { public static void main(String args[]){ } } Output Exception in thread "main" java.lang.Error: Unresolved compilation problem: at Sub.main(Sub.java:7)
Read MoreWhat are tokens in Java?
Java tokens are smallest elements of a program which are identified by the compiler. Tokens in java include identifiers, keywords, literals, operators and, separators.
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 MoreDo local variables in Java have default values?
No, local variables do not have default values. Once we create a local variable we must initialize it before using it. Since the local variables in Java are stored in stack in JVM there is a chance of getting the previous value as default value. Therefore, In Java default values for local variables are not allowed. Example public class Sample { public static void main(String args[] ){ int data; System.out.println(data); } } Error C:\Sample>javac Sample.java Sample.java:4: error: variable data might not have been initialized System.out.println(data); ^ 1 error
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