8305902: (cs) Resolve default Charset only once in StreamEncoder and StreamDecoder

Reviewed-by: alanb, bpb

Author: Sergey Tsypanov

src/java.base/share/classes/sun/nio/cs/StreamDecoder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -71,14 +71,10 @@ public static StreamDecoder forInputStreamReader(InputStream in,
                                                      String charsetName)
         throws UnsupportedEncodingException
     {
-        String csn = charsetName;
-        if (csn == null) {
-            csn = Charset.defaultCharset().name();
-        }
         try {
-            return new StreamDecoder(in, lock, Charset.forName(csn));
+            return new StreamDecoder(in, lock, Charset.forName(charsetName));
         } catch (IllegalCharsetNameException | UnsupportedCharsetException x) {
-            throw new UnsupportedEncodingException (csn);
+            throw new UnsupportedEncodingException (charsetName);
         }
     }
 

src/java.base/share/classes/sun/nio/cs/StreamEncoder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -58,14 +58,10 @@ public static StreamEncoder forOutputStreamWriter(OutputStream out,
                                                       String charsetName)
         throws UnsupportedEncodingException
     {
-        String csn = charsetName;
-        if (csn == null) {
-            csn = Charset.defaultCharset().name();
-        }
         try {
-            return new StreamEncoder(out, lock, Charset.forName(csn));
+            return new StreamEncoder(out, lock, Charset.forName(charsetName));
         } catch (IllegalCharsetNameException | UnsupportedCharsetException x) {
-            throw new UnsupportedEncodingException (csn);
+            throw new UnsupportedEncodingException (charsetName);
         }
     }