// Array-based list implementation
class AList<E> implements List<E> {
  private E listArray[];                  // Array holding list elements
  private static final int DEFAULT_SIZE = 10; // Default size
  private int maxSize;                    // Maximum size of list
  private int listSize;                   // Current # of list items
  private int curr;                       // Position of current element

  // Constructors
  // Create a new list object with maximum size "size"
  @SuppressWarnings("unchecked") // Generic array allocation
  AList(int size) {
    maxSize = size;
    listSize = curr = 0;
    listArray = (E[])new Object[size];         // Create listArray
  }
  // Create a list with the default capacity
  AList() {
    this(DEFAULT_SIZE);                   // Just call the other constructor
  }

  public void clear() {                    // Reinitialize the list
    listSize = curr = 0;               // Simply reinitialize values
  }

  // Insert "it" at current position
  public boolean insert(E it) {
    if (listSize >= maxSize) {
      return false;
    }
    for (int i=listSize; i>curr; i--) {  // Shift elements up
      listArray[i] = listArray[i-1];   //   to make room
    }
    listArray[curr] = it;
    listSize++;                        // Increment list size
    return true;
  }

  // Append "it" to list
  public boolean append(E it) {
    if (listSize >= maxSize) {
      return false;
    }
    listArray[listSize++] = it;
    return true;
  }

  // Remove and return the current element
  public E remove() {
    if ((curr<0) || (curr>=listSize)) {  // No current element
      return null;
    }
    E it = listArray[curr];            // Copy the element
    for(int i=curr; i<listSize-1; i++) {// Shift them down
      listArray[i] = listArray[i+1];
    }
    listSize--;                        // Decrement size
    return it;
  }

  public void moveToStart() {      // Set to front
    curr = 0; 
  }  
  public void moveToEnd() {  // Set at end
    curr = listSize; 
  } 
  public void prev() {  // Move left
    if (curr != 0) {
      curr--; 
    }
  }
  public void next() {  // Move right
    if (curr < listSize) {
      curr++; 
    }
  }
  public int length() {       // Return list size
    return listSize; 
  }
  public int currPos() {          // Return current position
    return curr; 
  }

  // Set current list position to "pos"
  public boolean moveToPos(int pos) {
    if ((pos < 0) || (pos > listSize)) {
      return false;
    }
    curr = pos;
    return true;
  }

  // Return true if current position is at end of the list
  public boolean isAtEnd() { 
    return curr == listSize; 
  }

  // Return the current element
  public E getValue() {
    if ((curr < 0) || (curr >= listSize)) // No current element
      return null;
    return listArray[curr];
  }
 
  //Tell if the list is empty or not
  public boolean isEmpty() {
    return listSize == 0;
  }
}

// Array-based list implementation
class AList implements List {
  private Object listArray[];             // Array holding list elements
  private static final int DEFAULT_SIZE = 10; // Default size
  private int maxSize;                    // Maximum size of list
  private int listSize;                   // Current # of list items
  private int curr;                       // Position of current element

  // Constructors
  // Create a new list object with maximum size "size"
  AList(int size) {
    maxSize = size;
    listSize = curr = 0;
    listArray = new Object[size];         // Create listArray
  }
  // Create a list with the default capacity
  AList() { this(DEFAULT_SIZE); }          // Just call the other constructor

  public void clear()                     // Reinitialize the list
    { listSize = curr = 0; }              // Simply reinitialize values

  // Insert "it" at current position
  public boolean insert(Object it) {
    if (listSize >= maxSize) return false;
    for (int i=listSize; i>curr; i--)  // Shift elements up
      listArray[i] = listArray[i-1];   //   to make room
    listArray[curr] = it;
    listSize++;                        // Increment list size
    return true;
  }

  // Append "it" to list
  public boolean append(Object it) {
    if (listSize >= maxSize) return false;
    listArray[listSize++] = it;
    return true;
  }

  // Remove and return the current element
  public Object remove() {
    if ((curr<0) || (curr>=listSize))  // No current element
      return null;
    Object it = listArray[curr];       // Copy the element
    for(int i=curr; i<listSize-1; i++) // Shift them down
      listArray[i] = listArray[i+1];
    listSize--;                        // Decrement size
    return it;
  }

  public void moveToStart() { curr = 0; }       // Set to front
  public void moveToEnd() { curr = listSize; }  // Set at end
  public void prev() { if (curr != 0) curr--; } // Move left
  public void next() { if (curr < listSize) curr++; } // Move right
  public int length() { return listSize; }      // Return list size
  public int currPos() { return curr; }         // Return current position

  // Set current list position to "pos"
  public boolean moveToPos(int pos) {
    if ((pos < 0) || (pos > listSize)) return false;
    curr = pos;
    return true;
  }

  // Return true if current position is at end of the list
  public boolean isAtEnd() { return curr == listSize; }

  // Return the current element
  public Object getValue() {
    if ((curr < 0) || (curr >= listSize)) // No current element
      return null;
    return listArray[curr];
  }
  
  // Check if the list is empty
  public boolean isEmpty() { return listSize == 0; }
}