127 lines
3.1 KiB
Java
127 lines
3.1 KiB
Java
package DataStructures.Bags;
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import java.util.Iterator;
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import java.util.NoSuchElementException;
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/**
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* Collection which does not allow removing elements (only collect and iterate)
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*
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* @param <Element> - the generic type of an element in this bag
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*/
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public class Bag<Element> implements Iterable<Element> {
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private Node<Element> firstElement; // first element of the bag
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private int size; // size of bag
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private static class Node<Element> {
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private Element content;
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private Node<Element> nextElement;
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}
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/**
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* Create an empty bag
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*/
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public Bag() {
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firstElement = null;
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size = 0;
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}
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/**
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* @return true if this bag is empty, false otherwise
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*/
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public boolean isEmpty() {
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return firstElement == null;
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}
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/**
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* @return the number of elements
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*/
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public int size() {
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return size;
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}
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/**
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* @param element - the element to add
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*/
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public void add(Element element) {
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Node<Element> oldfirst = firstElement;
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firstElement = new Node<>();
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firstElement.content = element;
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firstElement.nextElement = oldfirst;
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size++;
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}
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/**
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* Checks if the bag contains a specific element
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*
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* @param element which you want to look for
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* @return true if bag contains element, otherwise false
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*/
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public boolean contains(Element element) {
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Iterator<Element> iterator = this.iterator();
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while (iterator.hasNext()) {
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if (iterator.next().equals(element)) {
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return true;
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}
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}
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return false;
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}
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/**
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* @return an iterator that iterates over the elements in this bag in arbitrary order
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*/
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public Iterator<Element> iterator() {
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return new ListIterator<>(firstElement);
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}
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@SuppressWarnings("hiding")
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private class ListIterator<Element> implements Iterator<Element> {
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private Node<Element> currentElement;
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public ListIterator(Node<Element> firstElement) {
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currentElement = firstElement;
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}
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public boolean hasNext() {
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return currentElement != null;
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}
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/**
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* remove is not allowed in a bag
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*/
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@Override
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public void remove() {
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throw new UnsupportedOperationException();
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}
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public Element next() {
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if (!hasNext())
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throw new NoSuchElementException();
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Element element = currentElement.content;
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currentElement = currentElement.nextElement;
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return element;
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}
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}
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/**
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* main-method for testing
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*/
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public static void main(String[] args) {
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Bag<String> bag = new Bag<>();
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bag.add("1");
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bag.add("1");
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bag.add("2");
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System.out.println("size of bag = " + bag.size());
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for (String s : bag) {
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System.out.println(s);
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}
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System.out.println(bag.contains(null));
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System.out.println(bag.contains("1"));
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System.out.println(bag.contains("3"));
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}
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}
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