Method "ofReal" was removed from the API.

src/test/java/org/apache/commons/math4/transform/FastFourierTransformerTest.java

diff --git a/src/test/java/org/apache/commons/math4/transform/FastFourierTransformerTest.java b/src/test/java/org/apache/commons/math4/transform/FastFourierTransformerTest.java
index 5a2f3ca..b49d964 100644
--- a/src/test/java/org/apache/commons/math4/transform/FastFourierTransformerTest.java
+++ b/src/test/java/org/apache/commons/math4/transform/FastFourierTransformerTest.java
@@ -301,7 +301,7 @@
         final Complex[] x = new Complex[n];
         for (int i = 0; i < n; i++) {
             final double t = min + i * (max - min) / n;
-            x[i] = Complex.ofReal(f.value(t));
+            x[i] = Complex.ofCartesian(f.value(t), 0);
         }
         final Complex[] expected;
         final double s;