Added Data Structures implementation in java

JAVA/collection/AbstractCollection.java

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+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package collection;
+
+/**
+ *
+ * @author Zohaib Hassan Soomro
+ */
+public abstract class AbstractCollection implements Collection {
+
+protected AbstractCollection() {
+}
+
+@Override
+public abstract boolean add(Object object);
+
+@Override
+public boolean isEmpty() {
+    return (size() == 0);
+}
+
+@Override
+public abstract Iterator iterator();
+
+public boolean remove(Object object) {
+    Iterator it = iterator();
+    if (object == null) {
+        while (it.hasNext()) {
+            if (it.next() == null) {
+                it.remove();
+                return true;
+            }
+        }
+    } else {
+        while (it.hasNext()) {
+            if (object.equals(it.next())) {
+                it.remove();
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+@Override
+public abstract int size();
+
+@Override
+public boolean contains(Object object) {
+    Iterator it = iterator();
+    if (object == null) {
+        while (it.hasNext()) {
+            if (it.next() == null) {
+                return true;
+            }
+        }
+    } else {
+        while (it.hasNext()) {
+            if (object.equals(it.next())) {
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+@Override
+public String toString() {
+    if (isEmpty()) {
+        return "[ ]";
+    }
+    Iterator it = iterator();
+    StringBuffer buffer = new StringBuffer("[" + it.next());
+    while (it.hasNext()) {
+        buffer.append("," + it.next());
+    }
+    return (buffer + "]");
+}
+
+@Override
+public void clear() {
+    for (Iterator it = iterator(); it.hasNext();) {
+        it.next();
+        it.remove();
+    }
+}
+
+}

JAVA/collection/ArrayCollection.java

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+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package collection;
+
+/**
+ *
+ * @author Zohaib Hassan Soomro
+ */
+public class ArrayCollection extends AbstractCollection {
+
+private final int INITIAL_LENGTH = 15;
+private int size;
+private Object[] a = new Object[INITIAL_LENGTH];
+
+@Override
+public boolean add(Object object) {
+    if (size == a.length) {
+        resizeArray();
+    }
+    a[size++] = object;
+    return true;
+}
+
+@Override
+public int size() {
+    return size;
+}
+
+@Override
+public Iterator iterator() {
+    return new Iterator() {
+    private int i = 0;    //index of current element
+    private boolean okToRemove = false;
+
+    @Override
+    public boolean hasNext() {
+        return (i < size);
+    }
+
+    @Override
+    public Object next() {
+        if (i == size) {
+            throw new RuntimeException();
+        }
+        okToRemove = true;
+        return a[i++];
+    }
+
+    @Override
+    public void remove() {
+        if (!okToRemove) {
+            throw new IllegalStateException();
+        }
+        a[--i] = a[--size];
+        okToRemove = false;
+    }
+    };
+}
+
+public void resizeArray() {
+    Object[] aa = a;
+    a = new Object[2 * aa.length];
+    System.arraycopy(aa, 0, a, 0, size);
+}
+
+}

JAVA/collection/Collection.java

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+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package collection;
+
+/**
+ *
+ * @author Zohaib Hassan Soomro
+ */
+public interface Collection {
+    public boolean add(Object object);
+    public void clear();
+    public boolean contains(Object object);
+    public boolean isEmpty();
+    public Iterator iterator();
+    public boolean remove(Object object);
+    public int size();
+}

JAVA/collection/Country.java

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+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package collection;
+
+/**
+ *
+ * @author Zohaib Hassan Soomro
+ */
+public class Country {
+
+private String name, language, iso;
+private int area, population;
+
+public Country(String name, String iso, String language, int area, int population) {
+    this.name = name;
+    this.language = language;
+    this.iso = iso;
+    this.area = area;
+    this.population = population;
+}
+
+@Override
+public String toString() {
+    return ("[" + name + "," + iso + "," + language + "," + area + "," + population + "]");
+}
+
+public String getValue(String key) {
+    //mechanism to find the country with this key
+    return ("[" + name + "," + iso + "," + language + "," + area + "," + population + "]");
+}
+
+public static void main(String[] args) {
+    Country pak = new Country("Pakistan", "PK", "Urdu", 333333, 3333333);
+    Country bang = new Country("Bangladesh", "BN", "Bengali", 4444, 44444);
+    Country ind = new Country("India", "IN", "Hindi", 555555, 555555);
+
+    System.out.println("Pakistan: " + pak);
+    System.out.println("Bangladesh: " + bang);
+    System.out.println("India: " + ind);
+}
+}

JAVA/collection/Iterator.java

@@ -0,0 +1,16 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package collection;
+
+/**
+ *
+ * @author Zohaib Hassan Soomro
+ */
+public interface Iterator {
+    public boolean hasNext();
+    public Object next();
+    public void remove();
+}

JAVA/collection/LinkedCollection.java

@@ -0,0 +1,83 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package collection;
+
+/**
+ *
+ * @author Zohaib Hassan Soomro
+ */
+public class LinkedCollection extends AbstractCollection {
+
+private int size;
+private Node head = new Node();
+
+@Override
+public boolean add(Object object) {
+    head.previous = head.previous.next = new Node(object, head.previous, head);
+    size++;
+    return true;
+}
+
+class Node {
+
+private Object object;
+private Node previous, next;
+
+public Node() {
+    previous = this;
+    next = this;
+}
+
+public Node(Object object, Node previous, Node next) {
+    this.object = object;
+    this.previous = previous;
+    this.next = next;
+}
+}
+
+@Override
+
+public Iterator iterator() {
+
+    return new Iterator() {
+    private boolean okToRemove = false;
+    Node cursor = head.next;
+
+    @Override
+    public boolean hasNext() {
+        return (cursor != head);
+    }
+
+    @Override
+    public Object next() {
+        if (cursor == head) {
+            throw new RuntimeException();
+        }
+        okToRemove = true;
+        Object obj = cursor.object;
+        cursor = cursor.next;
+        return obj;
+    }
+
+    @Override
+    public void remove() {
+        if (!okToRemove) {
+            throw new IllegalStateException();
+        }
+        cursor.previous = cursor.previous.previous;
+        cursor.previous.next = cursor;
+        size--;
+        okToRemove = false;
+    }
+    };
+}
+
+@Override
+public int size() {
+    return size;
+}
+
+}

JAVA/collection/TestMyCollection.java

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+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package collection;
+
+/**
+ *
+ * @author Zohaib Hassan Soomro
+ */
+public class TestMyCollection {
+
+public static void main(String[] args) {
+    ArrayCollection collection = new ArrayCollection();
+    System.out.println("ArrayCollection:");
+
+    collection.add("Hello!");
+    collection.add("boyz");
+    collection.add("and");
+    collection.add("girlz");
+    System.out.println(collection);
+    collection.remove("and");
+    System.out.println(collection);
+
+    System.out.println("\n\nLinkedCollection:");
+    LinkedCollection collection2 = new LinkedCollection();
+    collection2.add("Hello!");
+    collection2.add("boyz");
+    collection2.add("and");
+    collection2.add("girlz");
+    System.out.println(collection2);
+    collection2.remove("and");
+    System.out.println(collection2);
+
+    System.out.println("Contains: "+collection.contains("boyz"));
+    System.out.println("Contains: "+collection2.contains("and"));
+
+}
+
+}