Free Java Quiz Questions With Answers – Prepare Yourself For Interviews

Which Set class should be most popular in a multi-threading environment, considering performance constraint?

Which Map class should be most popular in a multi-threading environment, considering performance constraint?

Which allows the removal of elements from a collection?

What will be the output of given code
import java. util.Arrays;
import java. util.Comparator;
class Sorting implements Comparator
{
public int compare(Integer o1, Integer o2)
{
return o2. compareTo(o1);
}
}
public class abc {
public static void main (String…a)
{
Integer intArray[]= {2,3,1};
Arrays.sort(intArray, new Sorting());
for(int i: intArray)
{
System. out. print(i+””);
}
}
}

What will be the output of given code
import java.util.Iterator;
import java.util.Set;
import java.util.TreeSet;

public class ConcurrentSkipListMapTest {
public static void main (String args)
{
Set set = new TreeSet();
set.add(1);
set.add(“2”);
set.add(3);

Iterator iterator = set.iterator();
while (iterator. hasNext())
{
System. out. print(iterator. next()+””);
}
}

}

What will be the output of given code
import java.util.ArrayList;
import java.util. Iterator;
import java.util. List;

public class ArrayListTest {
public static void main (String args[])
{
List arrayList = new ArrayList();

arrayList.add(“a”);
arrayList.add(“b”);

Iterator iterator = arrayList.iterator();

while (iterator.hasNext())
{
System.out.println(iterator.next());
arrayList.add(“c”);
}
}
}

What will be the output of given code
import java.util.HashSet;
import java.util.Set;
public class HashSetTest
{
public static void main (String args[])
{
Set hashSet = new HashSet();
hashSet.add(“1”);
hashSet.add(1);
hashSet.add(null);
hashSet.add(“null”);
System.out.println(hashSet);
}

}

What will be the output of given code
mport java.util.IdentityHashMap;
import java.util.Map;

public class MyClass
{
public static void main(String args[])
{
Map identityHashMap = new IdentityHashMap();
identityHashMap.put(new String(“a”),”audi”);
identityHashMap.put(new String(“a”),”ferrari”);
System.out.println(identityHashMap);
}
}

What will be the output of given code
import java.util.HashMap;
import java.util.Map;

public class MyClass
{
public static void main(String args[])
{
Map hashMap = new HashMap();
hashMap.put(new String(“a”),”audi”);
hashMap.put(new String(“a”),”ferrari”);
System.out.println(hashMap);
}
}

Which permits the removal of elements from a collection?

The Comparator interface contains the method?

Which of those is synchronized?

Which offers the best performance?

Which of these is the most popularly used class as a key in a HashMap?

What should we use when add and remove operations are more frequent than get operations

Iterator returned by ArrayList is?

Iterator returned by LinkedList is?

Iterator returned by CopyOnWriteArrayList is?

Iterator returned by HashMap on key, value and entry are?