whether 2 arraylist is equal or not - arraylist

Question

public boolean isSymmetric(TreeNode A) {
if(A==null)
return true;
/* if(isSymmetric(A.left) && isSymmetric(A.right))
return 1;
else return 0;*/
ArrayList<Integer> al1= preorder(A);
System.out.println(al1);
al.clear();
//System.out.println("common "+al);
p=invertTree(A);
ArrayList<Integer> al2= preorder(p);
System.out.println(al2);
int i=0,j=0;
while(i<al1.size() && i<al2.size())
{
System.out.println(al1.get(i)+" "+al2.get(i));
if(al1.get(i)!=al2.get(i))
return false;
i++;
}
return true;
}
i am trying to compare whether 2 arraylist are having same elements in same sequence or not
Your input
[1,2,2,null,3,null,3]
stdout
[1, 2, -1, 3, -1, -1, 2, -1, 3, -1, -1] //printed al1
[1, 2, 3, -1, -1, -1, 2, 3, -1, -1, -1] //printed al2
1 1 2 2 3 3
-1 -1
-1 -1
-1 -1 2 2 3 3
-1 -1
-1 -1
-1 -1
//don't know how they are showing same elements
Output
true
Expected
false

Answer 1

Let's suppose that you have al1 and al2 ArrayLists. This is how you can check whether they are equal (same size and same values in all positions)
boolean same = true;
if ((al1 == null) != (al2 == null)) {
same = false;
}
if (al1.size() != al2.size()) {
same = false;
} else {
for (int i = 0; same && (same = al1.get(i).equals(al2.get(i)); i++);
//The result is in same
}