Added Java implementation

Author: kyscg

Math/eulers_totient_function/Java/etf.java

@@ -0,0 +1,34 @@
+// A simple java program to calculate 
+// Euler's Totient Function 
+import java.io.*; 
+  
+class GFG { 
+  
+    // Function to return GCD of a and b 
+    static int gcd(int a, int b) 
+    { 
+        if (a == 0) 
+            return b; 
+        return gcd(b % a, a); 
+    } 
+  
+    // A simple method to evaluate 
+    // Euler Totient Function 
+    static int phi(int n) 
+    { 
+        int result = 1; 
+        for (int i = 2; i < n; i++) 
+            if (gcd(i, n) == 1) 
+                result++; 
+        return result; 
+    } 
+  
+    // Driver code 
+    public static void main(String[] args) 
+    { 
+        int n; 
+  
+        for (n = 1; n <= 10; n++) 
+            System.out.println("phi(" + n + ") = " + phi(n)); 
+    } 
+}