Merge pull request #1272 from wesllhey/feature/dynamic-array

dynamic array data structure

DataStructures/DynamicArray/DynamicArray.java

@@ -0,0 +1,158 @@
+package DataStructures.DynamicArray;
+
+import java.util.Arrays;
+import java.util.ConcurrentModificationException;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.Objects;
+import java.util.function.Consumer;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+public class DynamicArray<E> implements Iterable<E> {
+
+    private int capacity = 10;
+
+    private int size = 0;
+
+    private Object[] elements;
+
+    public DynamicArray(final int capacity) {
+        this.capacity = capacity;
+        this.elements = new Object[this.capacity];
+    }
+
+    public DynamicArray() {
+        this.elements = new Object[this.capacity];
+    }
+
+    public int newCapacity() {
+        this.capacity <<= 1;
+
+        return this.capacity;
+    }
+
+    public void add(final E element) {
+        if (this.size == this.elements.length)
+            this.elements = Arrays.copyOf(this.elements, newCapacity());
+
+        this.elements[this.size] = element;
+        size++;
+    }
+
+    public void put(final int index, E element) {
+        Objects.checkIndex(index, this.size);
+
+        this.elements[index] = element;
+    }
+
+    public E get(final int index) {
+        return getElement(index);
+    }
+
+    public E remove(final int index) {
+        final E oldElement = getElement(index);
+        fastRemove(this.elements, index);
+
+        return oldElement;
+    }
+
+    public int size() {
+        return this.size;
+    }
+
+    public boolean isEmpty() {
+        return this.size == 0;
+    }
+
+    public Stream<E> stream() {
+        return StreamSupport.stream(spliterator(), false);
+    }
+
+    private void fastRemove(final Object[] elements, final int index) {
+        final int newSize = this.size - 1;
+
+        if (newSize > index)
+            System.arraycopy(elements, index + 1, elements, index, newSize - index);
+
+        elements[this.size = newSize] = null;
+    }
+
+    private E getElement(final int index) {
+        Objects.checkIndex(index, this.size);
+        return (E) this.elements[index];
+    }
+
+    @Override
+    public String toString() {
+        return Arrays.toString(Arrays.stream(this.elements).filter(Objects::nonNull).toArray());
+    }
+
+    @Override
+    public Iterator iterator() {
+        return new DynamicArrayIterator();
+    }
+
+    private class DynamicArrayIterator implements Iterator<E> {
+
+        private int cursor;
+
+        @Override
+        public boolean hasNext() {
+            return this.cursor != size;
+        }
+
+        @Override
+        public E next() {
+            if (this.cursor > DynamicArray.this.size) throw new NoSuchElementException();
+
+            if (this.cursor > DynamicArray.this.elements.length) throw new ConcurrentModificationException();
+
+            final E element = DynamicArray.this.getElement(this.cursor);
+
+            this.cursor++;
+
+            return element;
+        }
+
+        @Override
+        public void remove() {
+            if (this.cursor < 0) throw new IllegalStateException();
+
+            DynamicArray.this.remove(this.cursor);
+
+            this.cursor--;
+        }
+
+        @Override
+        public void forEachRemaining(Consumer<? super E> action) {
+            Objects.requireNonNull(action);
+
+            for (int i = 0; i < DynamicArray.this.size; i++) {
+                action.accept(DynamicArray.this.getElement(i));
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        DynamicArray<String> names = new DynamicArray<>();
+        names.add("Peubes");
+        names.add("Marley");
+
+        for (String name : names) {
+            System.out.println(name);
+        }
+
+        names.stream().forEach(System.out::println);
+
+        System.out.println(names);
+
+        System.out.println(names.size());
+
+        names.remove(0);
+
+        for (String name : names) {
+            System.out.println(name);
+        }
+    }
+}