8339017: Make a couple of fields in DoubleByte static

Reviewed-by: bpb, naoto

Author: Andrey Turbanov

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2009, 2024, 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
@@ -402,7 +402,7 @@ protected CoderResult decodeBufferLoop(ByteBuffer src, CharBuffer dst) {
                         else
                             currentState = SBCS;
                     } else {
-                        char c = UNMAPPABLE_DECODING;
+                        char c;
                         if (currentState == SBCS) {
                             c = b2cSB[b1];
                             if (c == UNMAPPABLE_DECODING)
@@ -452,7 +452,7 @@ public int decode(byte[] src, int sp, int len, char[] dst) {
                     else
                         currentState = SBCS;
                 } else {
-                    char c =  UNMAPPABLE_DECODING;
+                    char c;
                     if (currentState == SBCS) {
                         c = b2cSB[b1];
                         if (c == UNMAPPABLE_DECODING)
@@ -503,8 +503,8 @@ public Decoder_DBCSONLY(Charset cs, char[][] b2c, char[] b2cSB, int b2Min, int b
     // The only thing we need to "override" is to check SS2/SS3 and
     // return "malformed" if found
     public static class Decoder_EUC_SIM extends Decoder {
-        private final int SS2 =  0x8E;
-        private final int SS3 =  0x8F;
+        private static final int SS2 = 0x8E;
+        private static final int SS3 = 0x8F;
 
         public Decoder_EUC_SIM(Charset cs,
                                char[][] b2c, char[] b2cSB, int b2Min, int b2Max,
@@ -556,7 +556,7 @@ public int decode(byte[] src, int sp, int len, char[] dst) {
     public static class Encoder extends CharsetEncoder
                                 implements ArrayEncoder
     {
-        protected final int MAX_SINGLEBYTE = 0xff;
+        protected static final int MAX_SINGLEBYTE = 0xff;
         private final char[] c2b;
         private final char[] c2bIndex;
         protected Surrogate.Parser sgp;
@@ -659,7 +659,7 @@ protected CoderResult encodeBufferLoop(CharBuffer src, ByteBuffer dst) {
                         dst.put((byte)(bb));
                     } else {
                         if (dst.remaining() < 1)
-                        return CoderResult.OVERFLOW;
+                            return CoderResult.OVERFLOW;
                         dst.put((byte)bb);
                     }
                     mark++;