BAEL-3481 - updated with review comments.

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingDeque.java

@@ -1,8 +1,9 @@
 package com.baeldung.algorithms.balancedbrackets;
 
-import java.util.Stack;
+import java.util.Deque;
+import java.util.LinkedList;
 
-public class BalancedBracketsUsingStack {
+public class BalancedBracketsUsingDeque {
 
         public boolean isBalanced(String str) {
                 if (null == str || str.length() == 0 || ((str.length() % 2) != 0)) {
@@ -17,17 +18,17 @@ public class BalancedBracketsUsingStack {
                         }
                 }
 
-                Stack<Character> stack = new Stack<>();
+                Deque<Character> deque = new LinkedList<>();
                 for (char ch: str.toCharArray()) {
                         if (ch == '{' || ch == '[' || ch == '(') {
-                                stack.push(ch);
+                                deque.addFirst(ch);
                         } else {
-                                if ( !stack.isEmpty()
-                                        && ((stack.peek() == '{' && ch == '}')
-                                        || (stack.peek() == '[' && ch == ']')
-                                        || (stack.peek() == '(' && ch == ')')
+                                if ( !deque.isEmpty()
+                                        && ((deque.peekFirst() == '{' && ch == '}')
+                                        || (deque.peekFirst() == '[' && ch == ']')
+                                        || (deque.peekFirst() == '(' && ch == ')')
                                     )) {
-                                        stack.pop();
+                                        deque.removeFirst();
                                 } else {
                                         return false;
                                 }

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingDequeUnitTest.java

@@ -5,75 +5,75 @@ import org.junit.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
-public class BalancedBracketsUsingStackUnitTest {
-        private BalancedBracketsUsingStack balancedBracketsUsingStack;
+public class BalancedBracketsUsingDequeUnitTest {
+        private BalancedBracketsUsingDeque balancedBracketsUsingDeque;
 
         @Before
         public void setup() {
-                balancedBracketsUsingStack = new BalancedBracketsUsingStack();
+                balancedBracketsUsingDeque = new BalancedBracketsUsingDeque();
         }
 
 
         @Test
         public void givenNullInput_whenCheckingForBalance_shouldReturnFalse() {
-                boolean result = balancedBracketsUsingStack.isBalanced(null);
+                boolean result = balancedBracketsUsingDeque.isBalanced(null);
                 assertThat(result).isFalse();
         }
 
         @Test
         public void givenEmptyString_whenCheckingForBalance_shouldReturnFalse() {
-                boolean result = balancedBracketsUsingStack.isBalanced("");
+                boolean result = balancedBracketsUsingDeque.isBalanced("");
                 assertThat(result).isFalse();
         }
 
         @Test
         public void givenInvalidCharacterString_whenCheckingForBalance_shouldReturnFalse() {
-                boolean result = balancedBracketsUsingStack.isBalanced("abc[](){}");
+                boolean result = balancedBracketsUsingDeque.isBalanced("abc[](){}");
                 assertThat(result).isFalse();
         }
 
         @Test
         public void givenOddLengthString_whenCheckingForBalance_shouldReturnFalse() {
-                boolean result = balancedBracketsUsingStack.isBalanced("{{[]()}}}");
+                boolean result = balancedBracketsUsingDeque.isBalanced("{{[]()}}}");
                 assertThat(result).isFalse();
         }
 
         @Test
         public void givenEvenLengthString_whenCheckingForBalance_shouldReturnFalse() {
-                boolean result = balancedBracketsUsingStack.isBalanced("{{[]()}}}}");
+                boolean result = balancedBracketsUsingDeque.isBalanced("{{[]()}}}}");
                 assertThat(result).isFalse();
         }
 
         @Test
         public void givenEvenLengthUnbalancedString_whenCheckingForBalance_shouldReturnFalse() {
-                boolean result = balancedBracketsUsingStack.isBalanced("{[(])}");
+                boolean result = balancedBracketsUsingDeque.isBalanced("{[(])}");
                 assertThat(result).isFalse();
         }
 
 
         @Test
         public void givenEvenLengthBalancedString_whenCheckingForBalance_shouldReturnTrue() {
-                boolean result = balancedBracketsUsingStack.isBalanced("{[()]}");
+                boolean result = balancedBracketsUsingDeque.isBalanced("{[()]}");
                 assertThat(result).isTrue();
         }
 
         @Test
         public void givenBalancedString_whenCheckingForBalance_shouldReturnTrue() {
-                boolean result = balancedBracketsUsingStack.isBalanced("{{[[(())]]}}");
+                boolean result = balancedBracketsUsingDeque.isBalanced("{{[[(())]]}}");
                 assertThat(result).isTrue();
         }
 
 
         @Test
         public void givenAnotherBalancedString_whenCheckingForBalance_shouldReturnTrue() {
-                boolean result = balancedBracketsUsingStack.isBalanced("{{([])}}");
+                boolean result = balancedBracketsUsingDeque.isBalanced("{{([])}}");
                 assertThat(result).isTrue();
         }
 
 
         @Test
         public void givenUnBalancedString_whenCheckingForBalance_shouldReturnFalse() {
-                boolean result = balancedBracketsUsingStack.isBalanced("{{)[](}}");
+                boolean result = balancedBracketsUsingDeque.isBalanced("{{)[](}}");
                 assertThat(result).isFalse();
         }