Quiz on Java Wildcard

 Which type of wildcard should be used to relax the data type restriction ?

class Main {

public static void main ( String args [ ] )

{

List<String> list = Arrays.aslist(“Sunday”,”Monday”,”Tuesday”);

print(list);

List<Object> list2 = Arrays.aslist(“Sunday”,”Monday”,”Tuesday”);

print(list2);

public static void print(List<?extend numbers> list)

{

System.out.println(list);

}

}

}

What will be the output of the program ?

class WildCard {

public static void main ( String args [ ] )

{

List < int > list1 = Arrays.aslist(1,2,3,4,5);

show(list);

List <String> list2 = Arrays.aslist(“One”,”two”,”three”,”four”,”five”);

show(list2);

public static void show(List<?> list)

{

System.out.println(list);

}

}

}

What is the output of the program ?

 Which are the things used to decide the type of wildcard for the program ?

Which of the following is the correct syntax of  Unbounded wildcards in Java ?

class Unbounded {

public static void main ( String args [ ] )

{

List<Object> array1 = new ArrayList(“Integer”,”String”,”Character”);

print(array1);

List<Object> array2 = new ArrayList(1 , 10 , 11 , 10 , 12 , 20 );

print(array2);

public static void print(List < ? > list)

{

System.out.println(list);

}

}

}

What is the output of the program ?

Which of the following is not a correct syntax for  using wildcards in java ?

class Addition {

public static void main ( String args [ ] )

{

List < Integer > l1 = new ArrayList(10,8,6,4,2);

add(l1);

public static void add(List < ? extends Number > list)

{

int sum=0;

for( Number i : l1)

{

sum = sum+i;

}

system.out.println(sum);

}

}

What is the output of the program ?

class LowerBound {

public static void main ( String args [ ] )

{

List<Integer> l1 = Arrays.aslist(10,20,30,40,50);

display(l1);

List <Number> l2 = Arrays.aslist(10.00,20.00,30.00,40.00,50.00);

public static void display(List<?super>list)

{

System.out.println(list);

}

}

}

What is the output of the program ?

 Super keyword is used in which of the following wildcards ?

 class Main {

public static void main ( String args [ ] )

{

List < Object > list1 = new Arraylist(“String”,1,’c’);

print(list1);

List<Integer> list2 = new ArrayList(2 , 3, 6 , 18 , 108 );

print(list2);

public static void print(List<?> list)

{

System.out.println(list);

}

}

}

What is the output of the program ?

class Numbers {

public static void main ( String args [ ] )

{

List < Integer > l1 = new ArrayList(25 , 75 , 125 , 175 , 225 , 275 , 325);

add(l1);

public static void add(List < ? extends Number > list)

{

System.out.println(l1.size());

}

}

}

What is the output of the program ?

Which variable can be an in variable in Java ?

Which of the following is the correct syntax of Lower bound wildcards in Java ?

class Main {

public static void main ( String args [ ] )

{

List<Integer> array1 = Array.mylist(10,100,1000,10000,100000);

message(array1);

List<Double> array2 = Array.mylist(1.1,1.11,1.111,1.1111,1.11111);

text(array2);

public static void text( List < ? super > list )

{

System.out.println(list);

}

}

}

What is the error in the program ?