Question

Write a complete bag class implementation using linked implementation. The linked bag class name must be LinkedBag and name your test program as LinkedBagDemo. Your test program should include following test conditions:

1. Get the number of items currently in the bag

2. See whether the bag is full

3. See whether the bag is empty

4. Add a given object to the bag

5. Remove an unspecified (not random) object from the bag

6. Remove an occurrence of a particular object from the bag, if possible

7. Remove all objects from the bag

8. Count the number of times a certain object occurs in the bag

9. Test whether the bag contains a particular object

10. Look at all objects that are in the bag

=============================================

Node.java

public class Node<T>
{
        private T entry;
        private Node next;
        
        private Node(T entryPortion)
        {
                this(entryPortion, null);
        }
                
        private Node(T entryPortion, Node nextNode)
        {
                entry = entryPortion;
                next = nextNode;
        }
}

=======================================================

BagInterface.java

public interface BagInterface<T>
{
        public int getCurrentSize();
        public boolean isFull();
        public boolean isEmpty();
        public boolean add(T newEntry);
        public T remove();
    public boolean remove(T anEntry);
        public void clear();
        public int getFrequencyOf(T anEntry);
        public boolean contains(T anEntry);
        public T[] toArray();
} // end BagInterface

Answer 1

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code:

//LinkedBag.java

public class LinkedBag<T> implements BagInterface<T>

{

private class Node

{

T entry;

Node next;

Node(T entryPortion)

{

this(entryPortion, null);

}

Node(T entryPortion, Node nextNode)

{

entry = entryPortion;

next = nextNode;

}

}

private Node first; // beginning of bag

private int n; // number of elements in bag

private int maxsize=10; //max size of the bag

public LinkedBag() {

this.first = null;

this.n = 0;

}

public int getCurrentSize()

{

return this.n;

}

public boolean isFull()

{

return this.n==this.maxsize;

}

public boolean isEmpty()

{

return this.n==0;

}

public boolean add(T item) {

if(!isFull())

{

Node oldfirst = this.first;

this.first = new Node(item,oldfirst);

this.n++;

return true;

}

else

return false;

}

public T remove()

{

Node oldfirst = this.first;

this.first=oldfirst.next;

this.n--;

T rem=oldfirst.entry;

return rem;

}

public boolean contains(T anEntry)

{

Node tmp=this.first;

for(int i=0;i<n;i++)

{

if(tmp.entry==anEntry)

return true;

tmp=tmp.next;

}

return false;

}

public boolean remove(T anEntry)

{

Node tmp=this.first;

for(int i=0;i<n;i++)

{

if(tmp.entry==anEntry)

{

this.n--;

tmp=tmp.next;

return true;

}

tmp=tmp.next;

}

return false;

}

public void clear()

{

this.n=0;

this.first=null;

}

public int getFrequencyOf(T anEntry)

{

Node tmp=this.first;int ct=0;

for(int i=0;i<n;i++)

{

if(tmp.entry==anEntry)

ct++;

tmp=tmp.next;

}

return ct;

}

public T[] toArray()

{

T arr[]=(T[])java.lang.reflect.Array.newInstance(Integer.class,n);

Node tmp=this.first;

for(int i=0;i<n;i++)

{

arr[i]=tmp.entry;

tmp=tmp.next;

}

return arr;

}

}

/**

* LinkedBagDemo - test case of the class

*/

class LinkedBagDemo

{

public static void main(String[] args) {

LinkedBag<Integer> l=new LinkedBag<Integer>();

for(int i=0;i<3;i++)

{

System.out.println("adding "+i+" to bag");

l.add(i);

}

for(int i=0;i<10;i++)

if(l.contains(i))

{ System.out.println("frequency of "+i+" is "+l.getFrequencyOf(i));

System.out.println("removing: "+l.remove(i));

}

System.out.println("bag size is "+l.getCurrentSize());

if(l.isEmpty())

System.out.println("bag is empty");

else

System.out.println("bag is not empty");

}

}

output: