CS302 Exam 2 Spring 2013 Reference Solution

Part III: Write an instantiable class...

import java.util.ArrayList;
public class BackPack {

    private ArrayList<String> items;
    private String name;
    private boolean open;

    //REQUIRED PUBLIC MEMBERS (no additional public members may be added. 
     public BackPack(String name, boolean open) {
        this.name = name;
        this.open = open;
        this.items = new ArrayList<String>();
    }

    @Override
    public String toString() {
        String s = name + "'s backpack contains " + items.size() + " items, ";
        if ( open )
            return s + "and is open.";
        return s + "and is closed.";
    }

    public void addItem(String item) {  items.add(item);    }
    
    public void setOpen(boolean open) {     this.open = open;   }
    
    public boolean isOpen() { return open; }

    public int numItems() { return items.size(); }

    private String itemAt(int index) {
        if ( index >=0 && index < items.size() ) 
            return items.get(index);
        return null;
    }
} // end class BackPack