Remove multiply and divide methods accepting double from ComplexNumbe…

…r class

exercises/practice/complex-numbers/.meta/src/reference/java/ComplexNumber.java

@@ -1,7 +1,6 @@
 final class ComplexNumber {
 
     private final double real;
-
     private final double imaginary;
 
     ComplexNumber(double real, double imaginary) {
@@ -32,7 +31,10 @@ ComplexNumber subtract(ComplexNumber other) {
     }
 
     ComplexNumber divide(ComplexNumber other) {
-        return this.multiply(other.conjugate()).divide(Math.pow(other.abs(), 2));
+        double divisor = Math.pow(other.real, 2) + Math.pow(other.imaginary, 2);
+        return new ComplexNumber(
+            (real * other.real + imaginary * other.imaginary) / divisor,
+            (real * other.imaginary - imaginary * other.real) / divisor);
     }
 
     double abs() {
@@ -46,12 +48,4 @@ ComplexNumber conjugate() {
     ComplexNumber exponentialOf() {
         return new ComplexNumber(Math.cos(imaginary), Math.sin(imaginary)).multiply(Math.exp(real));
     }
-
-    private ComplexNumber divide(double factor) {
-        return new ComplexNumber(real / factor, imaginary / factor);
-    }
-
-    private ComplexNumber multiply(double factor) {
-        return new ComplexNumber(factor * real, factor * imaginary);
-    }
-}
+}

exercises/practice/complex-numbers/src/main/java/ComplexNumber.java

@@ -28,18 +28,10 @@ ComplexNumber multiply(ComplexNumber other) {
         throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
     }
 
-    ComplexNumber multiply(double factor) {
-        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
-    }
-
     ComplexNumber divide(ComplexNumber other) {
         throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
     }
 
-    ComplexNumber divide(double divisor) {
-        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
-    }
-
     ComplexNumber conjugate() {
         throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
     }