Quiz on Java Generics

Which of the following is not an advantage of Generics in Java ?

class Generic {

public static void main ( String args [ ] )

{

ArrayList<Integer> list = new ArrayList<Integer> ();

list.add(100);

list.add(200);

list.add(300);

String a = list.get(2);

System.out.println(a);

}

}

 class HashMap {

public static void main ( String args [ ] )

{

Map <Integer,String> map = new HashMap<Integer,String> ();

map.add(1,”one”);

map.add(2.”two”);

map.add(3.”three”);

Set<Map.Entry<Integer,String>> set=map.entrySet();  

Iterator<Map.Entry<Integer,String>> itr=set.iterator();  

while(itr.hasNext()){  

Map.Entry e=itr.next();

System.out.println(e.getKey()+” “+e.getValue());

}

}

Which of the following classes use Generic Classes ?

 class Generic < G >

{

G obj;

Generic  ( G obj )

{

this.obj = obj;

}

public G getObject ( ) {

return this.obj;

}

}

class Main {

public static void main ( String args [ ] )

{

Generic < Integer> obj1 = new Generic <Integer> (10);

System.out.println(obj1.getObject());

Generic <String> obj2 = new Generic <String> (“DataFlair”);

System.out.println(obj2.getObject());

}

}

class StringSample <S> {

S obj;

StringSample( S obj )

{

this.obj = obj;

}

void print( ) {

return this.obj;

}

}

class Main {

public static void main ( String args [ ] )

{

Generic <Integer> object = new Generic <Integer> (“Ten”);

System.out.println(object.print());

}

}

Which of the following methods are used to restrict the number of types of data for a class ?

class Demo < O , T >

O = object1;

T = object2;

Demo ( object1 , object2 )

{

this.object1 = object1;

this.object2 = object2;

 }

public void print ( object1 , object2 )

{

System.out.println( object1 + object2 );

}

}

class Main {

public static void main ( String args [ ] )

{

Demo < Integer , String > obj = new Demo < Integer , String > ( “Two” , 2 );

obj.print();

}

}

class GenericSample {

void method ( E element  ) 

{

System.out.println(element.getclass().getName());

}

}

public static void main ( String args [ ] )

{

method(“DataFlair”);

}

}

Which of the following is possible in Generic classes ?

class Error {

Error( obj ) {

this.obj = obj;

}

void display( obj )

{

System.out.println(obj);

}

}

class Main {

public static void main ( String args [ ] )

{

Error < String > object = new Error < String > (“10”);

object.display();

}

}

class DemoClass {

public <T> void genericsMethod(T data) {

        System.out.println(data);

      }

}

class Main {

public static void main(String args [ ] ) 

DemoClass demo = new DemoClass();

demo.<String>genericsMethod(“DataFlair”);

}

}

Which of the following is used to display the package in generic classes ?

 class Arraylist {

public static void main ( String args [ ] )

{

ArrayList <> a = new ArrayList<>  ();

a.add(“String”);

a.add(“Integer”);

a.add(2);

System.out.println(a.get(2));

}

}

class Sample < S , I >

S = obj1;

I = obj2;

Sample ( obj1 , obj2 )

{

this.obj1 = obj1;

this.obj2 = obj2;

}

public void text ( obj1 , obj2 )

{

System.out.println(obj1);

System.out.println(obj2);

}

}

class Main {

public static void main ( String args [ ] )

{

Sample < String , Integer > s = new Sample < String , Integer > ( “DataFlair” , 1 );

s.text();

}

}