In java I need help modifying the following sections size is

In java I need help modifying the following sections: size, isEmpy, contains. I am trying to do this without changing any declaration of any method. Thank you

public class BtST<Key, Value> {
private Node first;

  
private class Node {
private Key key;
private Value val;
private Node next;

public Node(Key key, Value val, Node next) {
this.key = key;
this.val = val;
this.next = next;
}
}

public BtST() {
}

public int size() {
       return 0;\\\\ ****
}

public boolean isEmpty() {
       return true; \\\\\\***
}

public boolean contains(Key key) {
if (key == null) throw new IllegalArgumentException(\"argument to contains() is null\");
       return false;\\\\\\\\ ***
}

public Value get(Key key) {
if (key == null) throw new IllegalArgumentException(\"argument to get() is null\");
for (Node x = first; x != null; x = x.next) {
if (key.equals(x.key))
return x.val;
}
return null;
}

public void put(Key key, Value val) {
if (key == null) throw new IllegalArgumentException(\"first argument to put() is null\");
if (val == null) {
delete(key);
return;
}

for (Node x = first; x != null; x = x.next) {
if (key.equals(x.key)) {
x.val = val;
return;
}
}
first = new Node(key, val, first);
}

public void delete(Key key) {
if (key == null) throw new IllegalArgumentException(\"argument to delete() is null\");
first = delete(first, key);
}

  
private Node delete(Node x, Key key) {
if (x == null) return null;
if (key.equals(x.key)) {
return x.next;
}
x.next = delete(x.next, key);
return x;
}

public Iterable<Key> keys() {
Queue<Key> queue = new Queue<Key>();
for (Node x = first; x != null; x = x.next)
queue.enqueue(x.key);
return queue;
}

}

Current output, L 11 P 10 M 9 X 7 H S R 3 A 8 12 size mpty at does not contain A st doe not contain B St does not conta1n C gt does nat contain D at does not contain E st doe not contain F at does not cant G st does not contain H at does not contain I st doe not contain J su does not contain K st does not contain L at does not contain M at does not contain N s does not contain st does not contain P at does not contain at does not contain R St does not contain S st does not contain T gt does nat contain U st does not contain V St does not contain St does not conta1n X gt does nat contain Y et does not contain 2 Correct output, L 11 P 10 M 9 X 7 H 5. C 4 R 3 A 8 E 12 5 0 st is not empty st does contain A st does not contain B st does contai st does not contain D st does contain E st does not contain F st does not contain G st does contain H st does not contain I st does not contain J st does not contain K st does contain L st does contai n M st does not contain N st does not contain 0 st does contain P st does not contain Q st does contain R st does contain 5 st does not contain T st does not contain U st does not contain V st does not contai n W st does contai st does not contain Y st does not contain Z

Solution

public int size() {
     
      int s=0;
      Node temp=first;
      if(first==null)
   {  
       return 0;
      
   }
   else
   {  
          s++;
          while(temp.next!=null)
          {
           s++;
           temp=temp.next;
          }
          return s;
   }
  
}

public boolean isEmpty() {
     
       if(first==null) return true;
       else return false;
}

public boolean contains(Key key) {
   if (key == null) throw new IllegalArgumentException(\"argument to contains() is null\");
  
   Node temp=first;
   if(temp==null)
       return false;
   else
   {
       if(temp.key.equals(key)) ////////////////this statement is dependent on Key classs. You may have to override .equals() method to make this work
          return true;
       else
       {
          while(temp.next!=null)
          {
          
           temp=temp.next;
           if(temp.key.equals(key)) return true;
          }
      
          return false;
      
      
       }
  
  
     
}