feat: ArrayStack 초기화 예제 코드 작성

Author: ksundong

yoonexample/src/main/java/stack/ArrayStack.java

@@ -0,0 +1,39 @@
+package stack;
+
+public class ArrayStack<E> implements Stack<E> {
+
+  private static final int INITIAL_CAPACITY = 100;
+
+  private int topIndex;
+  private Object[] arr;
+
+  public ArrayStack() {
+    this.topIndex = -1;
+    this.arr = new Object[INITIAL_CAPACITY];
+  }
+
+  @Override
+  public int size() {
+    return this.topIndex + 1;
+  }
+
+  @Override
+  public boolean isEmpty() {
+    return this.topIndex == -1;
+  }
+
+  @Override
+  public void push(E data) {
+
+  }
+
+  @Override
+  public E pop() {
+    return null;
+  }
+
+  @Override
+  public E peek() {
+    return null;
+  }
+}