Which two statements are true about comparing two instances of the same class, given that the equals() and hashCode() methods have been properly overridden?

1. If the equals() method returns true, the hashCode() comparison == must return true.
2. If the equals() method returns false, the hashCode() comparison != must return true.
3. If the hashCode() comparison == returns true, the equals() method must return true.
4. If the hashCode() comparison == returns true, the equals() method might return true.

public static void main(String[] args) 
{
    Object obj = new Object() 
    {
        public int hashCode() 
        {
            return 42;
        }
    }; 
    System.out.println(obj.hashCode()); 
}

public class Test 
{ 
    public static void main (String[] args) 
    {
        String foo = args[1]; 
        String bar = args[2]; 
        String baz = args[3]; 
        System.out.println("baz = " + baz); /* Line 8 */
    } 
}

> java Test red green blue

public class Test 
{ 
    public static void main (String args[]) 
    {
        String str = NULL; 
        System.out.println(str); 
    } 
}

import java.util.*; 
class I 
{
    public static void main (String[] args) 
    {
        Object i = new ArrayList().iterator(); 
        System.out.print((i instanceof List)+","); 
        System.out.print((i instanceof Iterator)+","); 
        System.out.print(i instanceof ListIterator); 
    } 
}

public class Test 
{ 
    private static float[] f = new float[2]; 
    public static void main (String[] args) 
    {
        System.out.println("f[0] = " + f[0]); 
    } 
}

x = 0;
if (x1.hashCode() != x2.hashCode() )  x = x + 1;
if (x3.equals(x4) )  x = x + 10;
if (!x5.equals(x6) ) x = x + 100;
if (x7.hashCode() == x8.hashCode() )  x = x + 1000;
System.out.println("x = " + x);

1. hashCode() doesn't have to be overridden if equals() is.
2. equals() doesn't have to be overridden if hashCode() is.
3. hashCode() can always return the same value, regardless of the object that invoked it.
4. equals() can be true even if it's comparing different objects.

1. The Iterator interface declares only three methods: hasNext, next and remove.
2. The ListIterator interface extends both the List and Iterator interfaces.
3. The ListIterator interface provides forward and backward iteration capabilities.
4. The ListIterator interface provides the ability to modify the List during iteration.
5. The ListIterator interface provides the ability to determine its position in the List.