Finish implementation of dynamic array

Author: cszach

README.md

@@ -7,7 +7,7 @@ Java data structures
 Lists
 -----
 
-- [ ] Dynamic array
+- [x] Dynamic array
 - [x] Singly linked list
 - [ ] Doubly linked list
 - [ ] Queue

lists/DynamicArray.java

@@ -26,25 +26,42 @@ public int getSize() {
     return this.size;
   }
 
+  /** Shrinks the capacity of the underlying fixed-size array to free unused memory. */
+  public void shrinkSize() {
+    T[] newArray = (T[]) new Object[this.size];
+    for (int i = 0; i < this.size; i++) newArray[i] = this.array[i];
+    this.array = newArray;
+  }
+
+  /** Doubles the capacity of the underlying fixed-size array. */
+  public void growSize() {
+    T[] newArray = (T[]) new Object[this.array.length * 2];
+    for (int i = 0; i < this.size; i++) newArray[i] = this.array[i];
+    this.array = newArray;
+  }
+
   /**
    * Adds a new element to the end of this dynamic array.
    *
    * @param e the new element to be added to the end
    */
   public void add(T e) {
-    // Create a new fixed-length array with doubled capacity when space is run
-    // out
-    if (this.size + 1 > this.array.length) {
-      T[] newArray = (T[]) new Object[this.array.length * 2]; // double in size
-
-      for (int i = 0; i < this.size; i++) newArray[i] = this.array[i];
-
-      this.array = newArray;
-    }
-
+    if (this.size + 1 > this.array.length) this.growSize();
     this.array[this.size++] = e;
   }
 
+  /**
+   * Adds a new element at the specified index in this dynamic array.
+   *
+   * @param e the new element to be added at the specified index
+   * @param index the index to add the new element at
+   */
+  public void add(T e, int index) {
+    if (this.size + 1 > this.array.length) this.growSize();
+    for (int i = this.size++; i > index; i--) this.array[i] = this.array[i - 1];
+    this.array[index] = e;
+  }
+
   /** Removes the last element in this dynamic array. */
   public void remove() {
     this.array[--this.size] = null;
@@ -70,4 +87,14 @@ public void removeAt(int index) {
   public T getAt(int index) {
     return (T) this.array[index];
   }
+
+  /**
+   * Prints elements in the specified dynamic array line-by-line.
+   *
+   * @param array the dynamic array to be printed
+   */
+  public static void printDynamicArray(DynamicArray array) {
+    for (int i = 0; i < array.getSize(); i++)
+      System.out.println(array.getAt(i));
+  }
 }