added queue using stack and simple factorial program

Java/Factorial.java

@@ -0,0 +1,16 @@
+import java.util.*;
+public class Factorial {
+ public static void main(String args[])
+ {
+ Scanner sc=new Scanner(System.in);
+ int n,i,fact=1;
+ System.out.println("Enter a number:");
+ n=sc.nextInt();
+ for(i=1;i<=n;i++)
+ {
+ fact=fact*i;
+ }
+ System.out.println("Factorial:"+fact);
+ }
+
+}

Java/QueueUsingStack.java

@@ -0,0 +1,59 @@
+import java.util.*; 
+
+class QueueUsingStack 
+{ 
+static class Queue 
+{ 
+ static Stack<Integer> s1 = new Stack<Integer>(); 
+ static Stack<Integer> s2 = new Stack<Integer>(); 
+
+ static void enQueue(int x) 
+ { 
+ // Move all elements from s1 to s2 
+ while (!s1.isEmpty()) 
+ { 
+ s2.push(s1.pop()); 
+ //s1.pop(); 
+ } 
+
+ // Push item into s1 
+ s1.push(x); 
+
+ // Push everything back to s1 
+ while (!s2.isEmpty()) 
+ { 
+ s1.push(s2.pop()); 
+ //s2.pop(); 
+ } 
+ } 
+
+ // Dequeue an item from the queue 
+ static int deQueue() 
+ { 
+ // if first stack is empty 
+ if (s1.isEmpty()) 
+ { 
+ System.out.println("Q is Empty"); 
+ System.exit(0); 
+ } 
+
+ // Return top of s1 
+ int x = s1.peek(); 
+ s1.pop(); 
+ return x; 
+ } 
+}; 
+
+// Driver code 
+public static void main(String[] args) 
+{ 
+ Queue q = new Queue(); 
+ q.enQueue(1); 
+ q.enQueue(2); 
+ q.enQueue(3); 
+
+ System.out.println(q.deQueue()); 
+ System.out.println(q.deQueue()); 
+ System.out.println(q.deQueue()); 
+} 
+}