Add Infix to Postfix Converter using Stack (Java)

InfixToPostfix.java

@@ -0,0 +1,72 @@
+import java.util.Stack;
+
+/**
+ * This class converts an infix expression (e.g. A+B*C)
+ * into a postfix expression (e.g. A B C * +)
+ * using the Stack data structure.
+ *
+ * Time Complexity: O(n)
+ * Space Complexity: O(n)
+ */
+public class InfixToPostfix {
+
+    private static boolean isOperand(char c) {
+        return Character.isLetterOrDigit(c);
+    }
+
+    private static int precedence(char op) {
+        switch (op) {
+            case '^': return 3;
+            case '*': case '/': return 2;
+            case '+': case '-': return 1;
+            default: return -1;
+        }
+    }
+
+    public static String convert(String exp) {
+        StringBuilder result = new StringBuilder();
+        Stack<Character> stack = new Stack<>();
+
+        for (int i = 0; i < exp.length(); i++) {
+            char c = exp.charAt(i);
+
+            // Operand → add to result
+            if (isOperand(c)) {
+                result.append(c);
+            }
+            // Opening parenthesis
+            else if (c == '(') {
+                stack.push(c);
+            }
+            // Closing parenthesis
+            else if (c == ')') {
+                while (!stack.isEmpty() && stack.peek() != '(') {
+                    result.append(stack.pop());
+                }
+                if (!stack.isEmpty() && stack.peek() == '(') {
+                    stack.pop();
+                }
+            }
+            // Operator
+            else {
+                while (!stack.isEmpty() && precedence(stack.peek()) >= precedence(c)) {
+                    result.append(stack.pop());
+                }
+                stack.push(c);
+            }
+        }
+
+        // Pop remaining operators
+        while (!stack.isEmpty()) {
+            result.append(stack.pop());
+        }
+
+        return result.toString();
+    }
+
+    public static void main(String[] args) {
+        String exp = "A+B*C";
+        System.out.println("Infix: " + exp);
+        System.out.println("Postfix: " + convert(exp));
+    }
+}