Improve comments

Author: AlanBateman

src/java.base/share/classes/java/io/BufferedOutputStream.java

@@ -115,7 +115,8 @@ private void flushBuffer() throws IOException {
 
     /**
      * Grow buf to fit an additional len bytes if needed.
-     * A no-op if the buffer is not resizable.
+     * If possible, it grows by len+1 to avoid flushing when len bytes
+     * are added. A no-op if the buffer is not resizable.
      */
     private void growIfNeeded(int len) {
         if (maxBufSize > 0) {

src/java.base/share/classes/java/io/BufferedWriter.java

@@ -126,7 +126,8 @@ private void ensureOpen() throws IOException {
 
     /**
      * Grow char array to fit an additional len characters if needed.
-     * If possible, it grows by len+1 to reduce the need to flush.
+     * If possible, it grows by len+1 to avoid flushing when len chars
+     * are added.
      */
     private void growIfNeeded(int len) {
         int neededSize = nextChar + len + 1;