Question

Could I please get explainations and working out as to how to get to the answers.

Note that  is where part of the answer goes.

1.

Complete the following function that returns true if ArrayLists list1 and list2 are exactly the same in terms of contents
(same items in same order), false otherwise.
public static  sameSame(ArrayList<Integer> list1, ArrayList<Integer> list2) {
if(list1 == null || list2 == null)
return false;
if(  !=  )
return false;
for(int i=0; i < list1.size(); i++) {
if(  .equals(  )==false) {
return  ;
}
}
return  ;
}

2.

Complete the missing statements so that the output of the following code is:
[[10, 70, 20, 90], null, [50, 80]]
Do NOT include spaces in your answer!
ArrayList<Integer> b = new ArrayList<Integer>(Arrays.asList(10,888,20,90));
ArrayList<Integer> a = null;
ArrayList<Integer> c =  ; //make a reference copy only!
b.set(1, 70);
b = new ArrayList<Integer>(Arrays.asList(50, 80));
ArrayList<  > list = new ArrayList<  >();
list.add(  );
list.add(  );
list.add(  );
System.out.println(list);

Answer 1

1) //Here we need use boolean as return type, because we need to return the value true or false, which states whether list1 and list2 are same or different
   public static boolean sameSame(ArrayList<Integer> list1, ArrayList<Integer> list2) {
       if(list1 == null || list2 == null)
           return false;
      
       //If the number of elements in the lists are different, we can say that lists are not same. So, here we are checking the size of the lists and if their sizes are not equal, we are returning false.
       if( list1.size() != list2.size() )
           return false;
      
       for(int i=0; i < list1.size(); i++) {
           //In the question it is mentioned that both the lists should contain same items in same order. So, we are comparing the values in list1 with the elements in list2 at same index(i). Here i moves from index 0 to the index before end of the list.
           if( (list1.get(i)).equals(list2.get(i) )==false) {
               //If any of the values in the lists does not match, we return false.
               return false;
           }
       }
       //The program execution reaches this place, only if both the lists are not empty, and their sizes are same and all their element values are same in same order. So, here we return true.
       return true;
   }

2) ArrayList<Integer> b = new ArrayList<Integer>(Arrays.asList(10,888,20,90));
       ArrayList<Integer> a = null;
       //We are assigning array 'b' to 'c', because the value of array 'b' is changing to [50,80] later. To preserve current value of array 'b', we are creating a reference to array 'b' using 'c'. Here the value of array 'b' and 'c' is (10,888,20,90).
       ArrayList<Integer> c = b ; //make a reference copy only!
       //Here the value at index 1 of array 'b', which is 888, is set to 70. So, now the value of array 'b' and 'c' is (10,70,20,90).
       b.set(1, 70);
       //Here value of array 'b' is reassigned to (50,80). But value of array 'c' is (10,70,20,90) as it is pointing to previous list of array 'b'.
       b = new ArrayList<Integer>(Arrays.asList(50, 80));
       //Here we are adding the arrays 'a','b','c' to another list 'list'. As the datatype of arrays 'a','b','c' is ArrayList<Integer>, the ArrayList 'list' holding type should be 'ArrayList<Integer>'
       ArrayList< ArrayList<Integer> > list = new ArrayList< ArrayList<Integer> >();
       //As per the output, [10, 70, 20, 90] should be displayed first. So, we are adding the array 'c' which has these values.
       list.add( c );
       //As per the output, null should be displayed next. So, we are adding the array 'a' which has the null value.
       list.add( a );
       //As per the output, [50, 80] should be displayed next. So, we are adding the array 'b' which has these values.
       list.add( b );
       System.out.println(list);

Below is the complete program if you want to execute and check it:

ListsProgram.java:
import java.util.ArrayList;
import java.util.Arrays;

public class ListsProgram {
   public static void main(String args[]) {
       ArrayList<Integer> list1 = new ArrayList<Integer>(Arrays.asList(10,40,20,50,60,50));
       ArrayList<Integer> list2 = new ArrayList<Integer>(Arrays.asList(10,40,20,50,60,50));
       boolean result = sameSame(list1,list2);
       System.out.println("both are same:" + result);
      
       printArrays();
   }
  
   public static boolean sameSame(ArrayList<Integer> list1, ArrayList<Integer> list2) {
       if(list1 == null || list2 == null)
           return false;
      
       if( list1.size() != list2.size() )
           return false;
      
       for(int i=0; i < list1.size(); i++) {
           if( (list1.get(i)).equals(list2.get(i) )==false) {
               return false;
           }
       }
       return true;
   }
  
   public static void printArrays()
   {
       ArrayList<Integer> b = new ArrayList<Integer>(Arrays.asList(10,888,20,90));
       ArrayList<Integer> a = null;
       ArrayList<Integer> c = b ; //make a reference copy only!
       b.set(1, 70);
       b = new ArrayList<Integer>(Arrays.asList(50, 80));
       ArrayList< ArrayList<Integer> > list = new ArrayList< ArrayList<Integer> >();
       list.add( c );
       list.add( a );
       list.add( b );
       System.out.println(list);
   }
  
}