added java solution for modulo exponentiation

Author: Utkarsh Srivastava

Math/Fast Exponentiation with Mod/modulo_exponention.java

@@ -0,0 +1,30 @@
+import java.util.Scanner;
+
+public class Power {
+    public static int power(int x, int y, int p) 
+    { 
+        int ans = 1;      
+        x = x % p;  
+      
+        while (y > 0) 
+        { 
+            if((y & 1)==1) 
+                ans = (ans * x) % p;
+            y = y >> 1;  
+            x = (x * x) % p;  
+        } 
+        return ans; 
+    } 
+
+
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+
+        int x = sc.nextInt(); 
+        int y = sc.nextInt();
+        int m = sc.nextInt();
+        double ans = fast_expo(x, y, m);
+
+        System.out.println(ans);
+    }
+}