Article Categories
- All Categories
-
Data Structure
-
Networking
-
RDBMS
-
Operating System
-
Java
-
MS Excel
-
iOS
-
HTML
-
CSS
-
Android
-
Python
-
C Programming
-
C++
-
C#
-
MongoDB
-
MySQL
-
Javascript
-
PHP
-
Economics & Finance
Programming Articles
Page 2540 of 2547
What is string constant pool in Java?
When you store a String asString str1 = "Hello";directly, then JVM creates a String object with the given value in a separate block of memory known as String constant pool.And whenever we try to create another String asString str2 = "Hello";JVM verifies whether any String object with the same value exists in the String constant pool, if so, instead of creating a new object JVM assigns the reference of the existing object to the new variable.And when we store String asString str = new String("Hello");using the new keyword, a new object with the given value is created irrespective of the ...
Read MoreImmutable String in Java
In Java immutable objects are those whose data can’t be changed or modified (once modified). String class is immutable i.e. once we create a String object its data cannot be modified.
Read MoreHistory of C++ language
The C++ programming language has a history going back to 1979, when Bjarne Stroustrup was doing work for his Ph.D. thesis. He began work on "C with Classes", which as the name implies was meant to be a superset of the C language. His goal was to add object-oriented programming into the C language, which was and still is a language well-respected for its portability without sacrificing speed or low-level functionality.His language included classes, basic inheritance, inlining, default function arguments, and strong type checking in addition to all the features of the C language. The first C with Classes compiler ...
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 a Java array be declared as a static field, local variable or a method parameter?
We can declare an array as a local variable or method parameter but, an array cannot be static. Example public class Test{ public void sample(){ static int[] myArray = {20, 30}; System.out.println(); } public static void main(String args[]){ Test t = new Test(); t.sample(); } } Error C:\Sample>javac Test.java Test.java:3: error: illegal start of expression static int[] myArray = {20, 30}; ^ 1 error
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 does abstract modifier in Java do?
An abstract keyword is used to declare methods abstract methods and abstract classes. Once a method is declared abstract we should not specify body for those. Example public abstract class Sample{ public abstract demo(){ } } Error Sample.java:2: error: invalid method declaration; return type required public abstract demo(){ ^ 1 error And once a class is declared abstract it cannot be instantiated. Example public abstract class Sample{ public abstract void demo(); public static void main(String args[]){ new Sample(); } } Error C:\Sample>javac Sample.java Sample.java:4: error: Sample is abstract; cannot be instantiated new Sample(); ^ 1 error
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 ...
Read MoreCan access modifiers be used for local variables in Java?
Yes, a local variable can be public, private, protected or default.
Read MoreHow many ways a String object can be created in java?
You can create a String by − Step 1 − Assigning a string value wrapped in " " to a String type variable. String message = "Hello Welcome to Tutorialspoint"; Step 2 − Creating an object of the String class using the new keyword by passing the string value as a parameter of its constructor. String message = new String ("Hello Welcome to Tutorialspoint"); Step 3 − Passing a character array to the String constructor. char arr[] = {'H','e','l','l','o'}; String message = new String(arr);
Read More