Java/DataStructures/Bags/Bag.java at master · java66liu/Java · GitHub

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package DataStructures.Bags;

import java.util.Iterator;

import java.util.NoSuchElementException;

/**

* Collection which does not allow removing elements (only collect and iterate)

* @param <Element> - the generic type of an element in this bag

public class Bag<Element> implements Iterable<Element> {

private Node<Element> firstElement; // first element of the bag

private int size; // size of bag

private static class Node<Element> {

private Element content;

private Node<Element> nextElement;

}

/**

* Create an empty bag

public Bag() {

firstElement = null;

size = 0;

}

/**

* @return true if this bag is empty, false otherwise

public boolean isEmpty() {

return firstElement == null;

}

/**

* @return the number of elements

public int size() {

return size;

}

/**

* @param element - the element to add

public void add(Element element) {

Node<Element> oldfirst = firstElement;

firstElement = new Node<>();

firstElement.content = element;

firstElement.nextElement = oldfirst;

size++;

}

/**

* Checks if the bag contains a specific element

* @param element which you want to look for

* @return true if bag contains element, otherwise false

public boolean contains(Element element) {

Iterator<Element> iterator = this.iterator();

while (iterator.hasNext()) {

if (iterator.next().equals(element)) {

return true;

}

return false;

}

/**

* @return an iterator that iterates over the elements in this bag in arbitrary order

public Iterator<Element> iterator() {

return new ListIterator<>(firstElement);

}

@SuppressWarnings("hiding")

private class ListIterator<Element> implements Iterator<Element> {

private Node<Element> currentElement;

public ListIterator(Node<Element> firstElement) {

currentElement = firstElement;

}

public boolean hasNext() {

return currentElement != null;

}

/**

* remove is not allowed in a bag

@Override

public void remove() {

throw new UnsupportedOperationException();

}

public Element next() {

if (!hasNext())

throw new NoSuchElementException();

Element element = currentElement.content;

currentElement = currentElement.nextElement;

return element;

}

/**

* main-method for testing

public static void main(String[] args) {

Bag<String> bag = new Bag<>();

bag.add("1");

bag.add("2");

System.out.println("size of bag = " + bag.size());

for (String s : bag) {

System.out.println(s);

}

System.out.println(bag.contains(null));

System.out.println(bag.contains("1"));

System.out.println(bag.contains("3"));

}

Java/DataStructures/Bags/Bag.java at master · java66liu/Java · GitHub

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