Update StackArrayList.java

DataStructures/Stacks/StackArrayList.java

@@ -2,17 +2,16 @@ import java.util.ArrayList;
 
 /**
  * This class implements a Stack using an ArrayList.
- *
+ * <p>
  * 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.
- *
+ * <p>
  * 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{
+public class StackArrayList {
 
     /**
      * Main method
@@ -20,28 +19,31 @@ public class StackArrayList{
      * @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
+        StackArrayList myStackArrayList = new StackArrayList();
+        
         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.isEmpty()); // will print false
-    System.out.println(myStackArrayList.peek()); //will print 9
+        System.out.println(myStackArrayList.peek()); // will print 9
-    System.out.println(myStackArrayList.pop()); //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
+        System.out.println(myStackArrayList.pop()); // will print 2
     }
 
-  /** ArrayList representation of the stack */
+    /**
+     * ArrayList representation of the stack
+     */
     private ArrayList<Integer> stackList;
 
     /**
      * Constructor
      */
-  public StackArrayList(){
+    public StackArrayList() {
         stackList = new ArrayList<>();
     }
 
@@ -51,7 +53,7 @@ public class StackArrayList{
      *
      * @param value value to be added
      */
-  public void push(int value){
+    public void push(int value) {
         stackList.add(value);
     }
 
@@ -61,16 +63,15 @@ public class StackArrayList{
      *
      * @return Element popped
      */
-  public int pop(){
+    public int pop() {
 
-    if(!isEmpty()){ // checks for an empty Stack
+        if (!isEmpty()) { // checks for an empty Stack
-
+            int popValue = stackList.get(stackList.size() - 1);
-      int popValue=stackList.get(stackList.size()-1);
+            stackList.remove(stackList.size() - 1);  // removes the poped element from the list
-      stackList.remove(stackList.size()-1);  //removes the poped element from the list
             return popValue;
         }
 
-    System.out.print("The stack is already empty  ");
+        System.out.print("The stack is already empty!");
         return -1;
     }
 
@@ -79,7 +80,7 @@ public class StackArrayList{
      *
      * @return true if stack is empty
      */
-  public boolean isEmpty(){
+    public boolean isEmpty() {
         return stackList.isEmpty();
     }
 
@@ -88,7 +89,7 @@ public class StackArrayList{
      *
      * @return top element of stack
      */
-  public int peek(){
+    public int peek() {
-    return stackList.get(stackList.size()-1);
+        return stackList.get(stackList.size() - 1);
     }
 }