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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:

What is the use of super call?

Answer

By using super call we can call super class constructors  from sub class constructors and we can initialize super class private data.

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Subject: Java

Q:

What is the difference between path and classpath?

Answer

Path contains path of .exe files(commands).


Classpath contains path of packages. packages can be stored in folder or .jar files

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Subject: Java

Q:

What is JAR file? what are the main uses of JAR files?

Answer

JAR files are java's version of ZIP files. In fact, JAR uses the ZIP file format.


uses:


- to compress a number of . class files into one file


- to make a java executable JAR file.

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Subject: Java

Q:

What is unwrapping?

Answer

Unwrapping is also called as unpacking or unboxing.


Getting the private data stored in the object by using methods is called unpacking or unwrapping.

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Subject: Java

Q:

What is wrapping?

Answer

Wrapping is also called as packing or boxing.


Storing the data inside the object as private data which can accessed outside the class only by using methods.


 

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Subject: Java

Q:

What is different among String, StringBuffer, StringBuilder?

Answer

String class objects are immutable objects and they represents strings( sequence of characters)


StringBuffer class objects are mutable objects representing strings and they are Thread safe


StringBuild class objects are also mutable objects representing strings and they are not Thread safe

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Subject: Java