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

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packageBags;

importjava.util.Iterator;
importjava.util.NoSuchElementException;

/**
 * Collection which does not allow removing elements (only collect and iterate)
 *
 * @param <Element> - the generic type of an element in this bag
 */
publicclassBag<Element> implementsIterable<Element> {

privateNode<Element> firstElement; // first element of the bag
privateintsize; // size of bag

privatestaticclassNode<Element> {
privateElementcontent;
privateNode<Element> nextElement;
	}

/**
 * Create an empty bag
 */
publicBag() {
firstElement = null;
size = 0;
	}

/**
 * @return true if this bag is empty, false otherwise
 */
publicbooleanisEmpty() {
returnfirstElement == null;
	}

/**
 * @return the number of elements
 */
publicintsize() {
returnsize;
	}

/**
 * @param element - the element to add
 */
publicvoidadd(Elementelement) {
Node<Element> oldfirst = firstElement;
firstElement = newNode<>();
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
 */
publicbooleancontains(Elementelement) {
Iterator<Element> iterator = this.iterator();
while(iterator.hasNext()) {
if (iterator.next().equals(element)) {
returntrue;
 }
 }
returnfalse;
	}

/**
 * @return an iterator that iterates over the elements in this bag in arbitrary order
 */
publicIterator<Element> iterator() {
returnnewListIterator<>(firstElement);
	}

@SuppressWarnings("hiding")
privateclassListIterator<Element> implementsIterator<Element> {
privateNode<Element> currentElement;

publicListIterator(Node<Element> firstElement) {
currentElement = firstElement;
 }

publicbooleanhasNext() {
returncurrentElement != null;
 }

/**
 * remove is not allowed in a bag
 */
@Override
publicvoidremove() {
thrownewUnsupportedOperationException();
 }

publicElementnext() {
if (!hasNext())
thrownewNoSuchElementException();
Elementelement = currentElement.content;
currentElement = currentElement.nextElement;
returnelement;
 }
	}

/**
 * main-method for testing
 */
publicstaticvoidmain(String[] args) {
Bag<String> bag = newBag<>();

bag.add("1");
bag.add("1");
bag.add("2");

System.out.println("size of bag = " + bag.size());
for (Strings : bag) {
System.out.println(s);
 }

System.out.println(bag.contains(null));
System.out.println(bag.contains("1"));
System.out.println(bag.contains("3"));
	}

}