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Q:

How to create Directory on the HD?

Answer

To create directory on the HD we use mkDir() method:


boolean mkDir();


This method returns true if the directory is created on HD


This method returns false if the directory is already existing on HD

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Subject: Java

Q:

How to create a file on the hard disk by using File class object?

Answer

We can use the following method call:


boolean createNewFile();


This method creates a new file on the HD. 


 


If a file is already existing with the name given in the constructor then this method does not creates file on HD.


If file is successfully created then this method returns true.


If file is already existing on the HD then this method returns false.


This method may throw IOException whenever IO error is generated while creating file on HD.

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Subject: Java

Q:

What is the use of tostring() method?

Answer

If we print any object by using println() or print() methods.


The println() or print() methods internally calls tostring() method and prints the return value of toString() method.

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Subject: Java

Q:

What is the purpose of overriding toString() method?

Answer

we can override tostring() method to return String representation of our object data

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Subject: Java

Q:

What is the use of overloading ? or why overloading?

Answer

By using overloading we can add new functionality to the sub class.

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Subject: Java

Q:

What is the use of overriding?

Answer

- By using method overriding a sub class can change the definition of super class method.


- By using overriding a sub class can modify the functionality of the super class.

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Subject: Java

Q:

If sub class data member is hiding super class data member then how to access super class data member inside sub class methods?

Answer

use super keyword.


super keyword points immediate super class.


Class Sample {


int a =23;


 }


Class Sub extends Sample { 


 String a = "bablu";


 void show() {


 System.out.println(a); //bablu


 System. out. println(this.a); //bablu


 System. out.println(super.a); //23


}


}


Class Demo {


Public static void main(string[] args) {


sub s = new Sub();


s.show();


}


}


 

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Subject: Java

Q:

If super class ref is pointing sub class object then by using super class ref is it possible to call sub class newly defined method?

Answer

yes if the method is ovreriding method


no if the method is not overriding method

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Subject: Java