8263978: Clarify why 0 argument is ignored in SecureRandom::setSeed

wangweij · wangweij · commit 0b2aa1b6050e · 2021-03-23T22:23:37.000Z
Reviewed-by: valeriep
diff --git a/src/java.base/share/classes/java/security/SecureRandom.java b/src/java.base/share/classes/java/security/SecureRandom.java
@@ -730,10 +730,11 @@ public void setSeed(byte[] seed) {
     @Override
     public void setSeed(long seed) {
         /*
-         * Ignore call from super constructor (as well as any other calls
-         * unfortunate enough to be passing 0).  It's critical that we
-         * ignore call from superclass constructor, as digest has not
-         * yet been initialized at that point.
+         * Ignore call from super constructor as well as any other calls
+         * unfortunate enough to be passing 0. All SecureRandom
+         * constructors call `super(0)` which leads to `setSeed(0)`.
+         * We either keep the object unseeded (in `new SecureRandom()`)
+         * or we seed the object explicitly (in `new SecureRandom(byte[])`).
          */
         if (seed != 0) {
             setSeed(longToByteArray(seed));
