Queue via 2 stacks: done

Author: rampatra

src/main/java/com/ctci/stacksandqueues/QueueViaStacks.java

@@ -0,0 +1,59 @@
+package com.ctci.stacksandqueues;
+
+import java.util.NoSuchElementException;
+import java.util.Stack;
+
+/**
+ * @author rampatra
+ * @since 2019-02-06
+ */
+public class QueueViaStacks<T> {
+
+    private Stack<T> stackFront = new Stack<>();
+    private Stack<T> stackRear = new Stack<>();
+
+    private T add(T item) {
+        return stackRear.push(item);
+    }
+
+    private T remove() {
+        if (stackFront.empty() && stackRear.empty()) {
+            throw new NoSuchElementException();
+        } else if (!stackFront.empty()) {
+            return stackFront.pop();
+        } else {
+            while (!stackRear.empty()) {
+                stackFront.push(stackRear.pop());
+            }
+            return stackFront.pop();
+        }
+    }
+
+    private void print() {
+        Stack<T> tempStack = new Stack<>();
+        while (!stackFront.empty()) {
+            tempStack.push(stackFront.pop());
+        }
+        System.out.print("[");
+        tempStack.forEach(item -> System.out.print(item + ","));
+        stackRear.forEach(item -> System.out.print(item + ","));
+        System.out.println("]");
+        while (!tempStack.empty()) {
+            stackFront.push(tempStack.pop());
+        }
+    }
+
+    public static void main(String[] args) {
+        QueueViaStacks<Integer> queue = new QueueViaStacks<>();
+        queue.add(1);
+        queue.add(2);
+        queue.add(3);
+        queue.print();
+        queue.remove();
+        queue.print();
+        queue.remove();
+        queue.print();
+        queue.remove();
+        queue.print();
+    }
+}