implement Java 17 j.u.r.RandomGenerator#nextExponential()

Author: stefan-zobel

src/main/java/java9/util/SplittableRandom.java

@@ -843,6 +843,22 @@ public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound)
              false);
     }
 
+    /**
+     * Returns a nonnegative {@code double} value pseudorandomly chosen from
+     * an exponential distribution whose mean is 1.
+     *
+     * @return a nonnegative {@code double} value pseudorandomly chosen from an
+     *         exponential distribution
+     * @since 17
+     */
+    public double nextExponential() {
+        double u;
+        do {
+            u = nextDouble();
+        } while (u == 0.0 || u == 1.0);
+        return -Math.log(u);
+    }
+
     /**
      * Return true if the implementation of RandomGenerator (algorithm) has been
      * marked for deprecation.
@@ -856,7 +872,6 @@ public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound)
      *
      * @return true if the implementation of RandomGenerator (algorithm) has been
      *         marked for deprecation
-     *
      * @since 17
      */
     public boolean isDeprecated() {

src/main/java/java9/util/concurrent/ThreadLocalRandom.java

@@ -729,6 +729,22 @@ public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound)
              false);
     }
 
+    /**
+     * Returns a nonnegative {@code double} value pseudorandomly chosen from
+     * an exponential distribution whose mean is 1.
+     *
+     * @return a nonnegative {@code double} value pseudorandomly chosen from an
+     *         exponential distribution
+     * @since 17
+     */
+    public double nextExponential() {
+        double u;
+        do {
+            u = nextDouble();
+        } while (u == 0.0 || u == 1.0);
+        return -Math.log(u);
+    }
+
     /**
      * Return true if the implementation of RandomGenerator (algorithm) has been
      * marked for deprecation.
@@ -742,7 +758,6 @@ public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound)
      *
      * @return true if the implementation of RandomGenerator (algorithm) has been
      *         marked for deprecation
-     *
      * @since 17
      */
     public boolean isDeprecated() {