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04/OurArrayIntList.java

+public class OurArrayList<E> implements IList<E> {
+    private E[] data;
+    private int size;
+
+    public OurArrayList(int initialCapacity) {
+        this.data = (E[])new Object[initialCapacity];
+        this.size = 0;
+    }
+
+    public OurArrayList() {
+        this(10);
+    }
+
+    public String toString() {
+        if (this.size == 0) {
+            return "[]";
+        }
+        String result = "[";
+        for (int i = 0; i < this.size; i++) {
+            result += this.data[i] + ", ";
+        }
+        result = result.substring(0, result.length() - 2);
+        return result + "]";
+    }
+
+    public void add(E element) {
+        this.add(this.size, element);
+    }
+
+    /**
+     * Puts element at index idx, shifting over everything after to the right.
+     * @param idx
+     * @param element
+     * For example, idx = 2, element = 42
+     * [1, 2, 3, 4, 5]
+     *        ^
+     * [1, 2, 42, 3, 4, 5]
+     */
+    public void add(int idx, E element) {
+        resize();
+        for (int i = this.size; i > idx; i--) {
+            this.data[i] = this.data[i-1];
+        }
+        this.data[idx] = element;
+        this.size++;
+    }
+
+    private void resize() {
+        // size vs. capacity < how much storage space in the list
+        // ^ how many elements in the list
+        // capacity == this.data.length
+        if (this.size == this.data.length) {
+            // Time to resize!
+            E[] newData = (E[])new Object[this.data.length * 2];
+            for (int i = 0; i < this.size; i++) {
+                newData[i] = this.data[i];
+            }
+            this.data = newData;
+        }
+    }
+
+    @Override
+    public int size() {
+        return this.size;
+    }
+
+    @Override
+    public void set(int idx, E elem) {
+        if (idx < 0 || idx >= this.size) {
+            throw new IllegalArgumentException(idx + " is not a valid index!");
+        }
+        this.data[idx] = elem;
+
+    }
+
+    public E get(int idx) {
+        if (idx < 0 || idx >= this.size) {
+            throw new IllegalArgumentException(idx + " is not a valid index!");
+        }
+        return this.data[idx];
+    }
+
+    @Override
+    public void clear() {
+        this.size = 0;
+    }
+}