From 6d96760d1377b527f71009bef4526b90c3a15bb6 Mon Sep 17 00:00:00 2001 From: David Hinske Date: Wed, 4 Oct 2017 13:57:26 +0200 Subject: [PATCH] addded Bag-datastructure --- data_structures/Bags/Bag.java | 126 ++++++++++++++++++++++++++++++++++ 1 file changed, 126 insertions(+) create mode 100644 data_structures/Bags/Bag.java diff --git a/data_structures/Bags/Bag.java b/data_structures/Bags/Bag.java new file mode 100644 index 000000000000..06b454ed907e --- /dev/null +++ b/data_structures/Bags/Bag.java @@ -0,0 +1,126 @@ +package Bags; + +import java.util.Iterator; +import java.util.NoSuchElementException; + +/** + * Collection which does not allow removing elements (only collect and iterate) + * + * @param - the generic type of an element in this bag + */ +public class Bag implements Iterable { + + private Node firstElement; // first element of the bag + private int size; // size of bag + + private static class Node { + private Element content; + private Node 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 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 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 iterator() { + return new ListIterator<>(firstElement); + } + + @SuppressWarnings("hiding") + private class ListIterator implements Iterator { + private Node currentElement; + + public ListIterator(Node 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 bag = new Bag<>(); + + bag.add("1"); + 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")); + } + +} pFad - Phonifier reborn

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