MyListArray

package com.files;


interface MyList<e> {
    //sentinels
    public boolean isEmpty();
    public boolean isFull();
    public boolean addItem(e item);
    public boolean isItem(e item);
    public boolean removeItem(e item);
    public boolean insertAfter(e item, e newitem);
    public boolean insertBefore(e item, e newitem);
    public boolean updateItem(e item, e newitem);

}// end of interface

class MyListArray<E> implements MyList<E>{

    private int size;
    private int count;
    private E[] entries;
    private int position;

    @SuppressWarnings("unchecked")
    public MyListArray(int size) {
        this.entries = (E[]) new Object[size];
    }

    public MyListArray() {  this(10);   }

    @Override
    public boolean isEmpty() {  return count == 0;  }

    @Override
    public boolean isFull() {   return count == entries.length; }

    @Override
    public boolean addItem(E item) {
        entries[count++] = item;
        return true;
    }

    @Override
    public boolean isItem(E item) {
        boolean found = false;
        for(int i=0; i<entries.length; i++) {
            if(item.equals(entries[i])) {
                found = true;
                position = i;
                break;
            }
        }
        return found;
    }

    @Override
    public boolean removeItem(E item) {
        boolean isElem = isItem(item);
        if(isElem) {
            for(int i=0; i<entries.length; i++) {
                if(i == 0) {
                    entries[0] = null;
                    count--;
                    break;
                }
            }
        }
        return isElem;
    }

    @Override
    public boolean insertAfter(E item, E newitem) {
        boolean isElem = isItem(item);
        if(isElem) {
            count++;
            for(int i=entries.length-1; i>position; i--) {
                entries[i] = entries[i-1];
            }
            entries[position+1] = newitem;
        }
        return isElem;
    }

    @Override
    public boolean insertBefore(E item, E newitem) {
        boolean isElem = isItem(item);
        if(isElem) {
            count++;
            for(int i=entries.length-1; i>position; i--) {
                entries[i] = entries[i-1];
            }
            entries[position] = newitem;
        }
        return isElem;
    }

    @Override
    public boolean updateItem(E item, E newitem) {
        boolean isElem = isItem(item);
        if(isElem) {
            for(int i=0; i<entries.length; i++) {
                if(position == i) {
                    entries[count++] = newitem;
                }
            }
        }
        return isElem;
    }

    public String toString() {
        StringBuffer sb = new StringBuffer();
        //sb.append(entries[0]);
        for(int i=0; i<entries.length; i++) {
            if(entries[i] != null) {
                sb.append(entries[i]+"->");
            }
        }
        return sb.toString();
    }

}//End of the class

public class TestList {
    static public void main(String... args){
          MyList<String> list = new MyListArray<String>();
             list.addItem(new String("A"));
             list.addItem(new String("B"));
             list.addItem(new String("C"));
             list.addItem(new String("D"));
             list.addItem(new String("E"));
             System.out.println(list);
             System.out.println("Remove the item in the head:");
             list.removeItem(new String("A"));
             System.out.println(list);
             System.out.println("Insert a new  item after tail:");
             list.insertAfter(new String("E"),new String("X"));
             System.out.println(list);
             System.out.println("Insert a new  item after any item not the tail:");
             list.insertAfter(new String("B"),new String("X"));
             System.out.println(list);
             System.out.println("Insert a new  item before head:");
             list.insertBefore(new String("B"),new String("W"));
             System.out.println(list);
             System.out.println("Insert a new  item ebfore any item not the head:");
             list.insertBefore(new String("D"),new String("W"));
             System.out.println(list);
             System.out.println("Update element D, changed it to Y");
             list.updateItem(new String("D"),new String("Y"));
             System.out.println(list);
    }
}//End of the class