Move code for Stack ArrayList from Stacks.java to StackArrayList.java

DataStructures/Stacks/StackArrayList.java

@@ -0,0 +1,94 @@
+import java.util.ArrayList;
+
+/**
+ * This class implements a Stack using an ArrayList.
+ *
+ * A stack is exactly what it sounds like. An element gets added to the top of
+ * the stack and only the element on the top may be removed.
+ *
+ * This is an ArrayList Implementation of a stack, where size is not
+ * a problem we can extend the stack as much as we want.
+ *
+ * @author Unknown
+ *
+ */
+public class StackArrayList{
+
+  /**
+   * Main method
+   *
+   * @param args Command line arguments
+   */
+  public static void main(String[] args) {
+    StackArrayList myStackArrayList = new StackArrayList(); //Declare a stack of maximum size 4
+    //Populate the stack
+    myStackArrayList.push(5);
+    myStackArrayList.push(8);
+    myStackArrayList.push(2);
+    myStackArrayList.push(9);
+
+    System.out.println("*********************Stack List Implementation*********************");
+    System.out.println(myStackArrayList.isEmpty()); //will print false
+    System.out.println(myStackArrayList.peek()); //will print 9
+    System.out.println(myStackArrayList.pop()); //will print 9
+    System.out.println(myStackArrayList.peek()); // will print 2
+    System.out.println(myStackArrayList.pop()); //will print 2
+  }
+
+  /** ArrayList representation of the stack */
+  private ArrayList<Integer> stackList;
+
+  /**
+   * Constructor
+   */
+  public StackArrayList(){
+    stackList = new ArrayList<>();
+  }
+
+  /**
+   * Adds value to the end of list which
+   * is the top for stack
+   *
+   * @param value value to be added
+   */
+  public void push(int value){
+    stackList.add(value);
+  }
+
+  /**
+   * Pops last element of list which is indeed
+   * the top for Stack
+   *
+   * @return Element popped
+   */
+  public int pop(){
+
+    if(!isEmpty()){ // checks for an empty Stack
+
+      int popValue=stackList.get(stackList.size()-1);
+      stackList.remove(stackList.size()-1);  //removes the poped element from the list
+      return popValue;
+    }
+
+    System.out.print("The stack is already empty  ");
+    return -1;
+  }
+
+  /**
+   * Checks for empty Stack
+   *
+   * @return true if stack is empty
+   */
+  public boolean isEmpty(){
+    return stackList.isEmpty();
+  }
+
+  /**
+   * Top element of stack
+   *
+   * @return top element of stack
+   */
+  public int peek(){
+    return stackList.get(stackList.size()-1);
+  }
+}