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Which interface should be implemented for sorting on basis of many criteria’s?

Can two threads on same ConcurrentHashMap object access it concurrently

LinkedHashSet implements:

What will be the output of the following code –
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArraySet;
public class CopyOnWriteArraySetTest
{
public static void main (String args[])
{
Set<String> copyOnWriteArraySet = new CopyOnWriteArraySet<String>();
copyOnWriteArraySet.add(” a “);
copyOnWriteArraySet.add ( ” b” );
Iterator<String> iterator = copyOnWriteArraySet.iterator();
while(iterator.hasNext())
{
copyOnWriteArraySet.add( ” c ” );
System.out.println(iterator.next());
}
}
}

In WeakHashMap

A EnumSet

Iterator returned by HashSet is

Iterator returned by CopyOnWriteArraySet is

Iterator returned by TreeSet is

Iterator returned by LinkedHashSet is

Iterator returned by ConcurrentSkipListSet is

Which List is synchronized?

Which Set is synchronized?

What will be the output of the following code –
import java.util.List;
import java.util.ListIterator;
import java.util.ArrayList;

public class ArrayListTest
{
public static void main (String args[])
{
List<String> arrayList = new ArrayList<String>();
arrayList.add(“a”);
arrayList.add(“b”);

ListIterator<String> listIterator = arrayList.listIterator();
while (listIterator.hasNext())
{
System.out.println(listIterator.next());
listIterator.previous( );
}
}

}

What is the significance of using instanceOf operator and getClass() in equals method?

What will be the output of the following code –
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentSkipListMap;

public class ConcurrentSkipMapTest {

public static void main (String args[])
{
Map<Integer,String> concurrentSkipListMap= new ConcurrentSkipListMap<Integer,String>();
concurrentSkipListMap.put(11,”audi”);
concurrentSkipListMap.put(44,”null”);

Iterator<Integer> keyIterator = concurrentSkipListMap.keySet().iterator();
while (keyIterator.hasNext())
{
System.out.print(keyIterator.next());

}
}

}

What will be the output of the following code –
import java.util.HashMap;
public class Employee {
private String name;

public Employee(String name)
{
this.name = name;
}
}

class EmployeeClass
{
public static void main(String args[])
{
HashMap<Employee,String> hm=new HashMap<Employee,String>();
hm.put(new Employee(“a”),”emp1″);
hm.put(new Employee(“b”),”emp2″);
hm.put(new Employee(“a”),”emp1 overridden”);

System.out.println(hm.size());
System.out.println(hm.get(new Employee(“a”)));
}

}