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diff --git a/challenge-159/cheok-yin-fung/java/Moebius.java b/challenge-159/cheok-yin-fung/java/Moebius.java
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+// The Weekly Challenge 159
+// Task 2 Moebius Function
+// Usage: java Moebius N
+
+public class Moebius
+{
+    public static void main(String[] args)
+    {
+        int N = 1;
+        try {
+            N = Integer.parseInt(args[0]);
+            if (N<=0)
+                throw new ArithmeticException(); 
+        } catch (Exception e) {
+            System.err.print("Please use a positive integer ");
+            System.err.println("as your parameter.");
+            System.exit(0);
+        }
+        double[][] complex1 = new double[][] { {1, 0} , {0, 1} };
+        double[][] complex2 = new double[][] { {0, 1} , {-1, 0} };
+        System.out.println(Math.round(mu(N)));
+    }
+
+
+    public static double mu(int n)
+    {
+        double[][] sum = ithRootOfUnityModuloN(1, n);
+        LOOP: for (int i=2; i<n; i++) 
+        {
+            for (int s=2; s<n; s++)
+            {
+                if ( (i*s) % n == 0 )
+                    continue LOOP;
+            }
+            sum = complexAddition(sum, ithRootOfUnityModuloN(i,n));
+        }
+        return sum[0][0];
+    }
+
+
+    public static double[][] complexAddition(double[][] c1, double[][] c2)
+    {
+        double a = c1[0][0];
+        double b = c1[0][1];
+        double c = c1[1][0];
+        double d = c1[1][1];
+        double e = c2[0][0];
+        double f = c2[0][1];
+        double g = c2[1][0];
+        double h = c2[1][1];
+        return new double[][] {{ a+e, b+f }, { c+g, d+h }};
+    }
+
+
+
+    public static double[][] complexMultiplication(double[][] c1, double[][] c2)
+    {
+        double a = c1[0][0];
+        double b = c1[0][1];
+        double c = c1[1][0];
+        double d = c1[1][1];
+        double e = c2[0][0];
+        double f = c2[0][1];
+        double g = c2[1][0];
+        double h = c2[1][1];
+        return new double[][] {{a*e+b*g, a*f+b*h}, {c*e+d*g, c*f+d*h}};
+    }
+
+
+
+    public static double[][] ithRootOfUnityModuloN(int i , int n)
+    {
+        double realPart = Math.cos(2*Math.PI*i/n);
+        double imaginaryPart = Math.sin(2*Math.PI*i/n);
+        double[][] result = new double[][] {
+                              {realPart, imaginaryPart},
+                              {-imaginaryPart, realPart}  
+                            };
+        return result;
+    }
+}