8314129: Make fields final in java.util.Scanner

src/java.base/share/classes/java/util/Scanner.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 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
@@ -25,17 +25,34 @@
 
 package java.util;
 
-import java.io.*;
-import java.math.*;
-import java.nio.*;
-import java.nio.channels.*;
-import java.nio.charset.*;
+import java.io.Closeable;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.StringReader;
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.nio.CharBuffer;
+import java.nio.channels.Channels;
+import java.nio.channels.ReadableByteChannel;
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.IllegalCharsetNameException;
+import java.nio.charset.UnsupportedCharsetException;
 import java.nio.file.Path;
 import java.nio.file.Files;
-import java.text.*;
+import java.text.DecimalFormat;
+import java.text.DecimalFormatSymbols;
+import java.text.NumberFormat;
 import java.text.spi.NumberFormatProvider;
 import java.util.function.Consumer;
-import java.util.regex.*;
+import java.util.regex.MatchResult;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import java.util.regex.PatternSyntaxException;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 import sun.util.locale.provider.LocaleProviderAdapter;
@@ -317,13 +334,13 @@ public final class Scanner implements Iterator<String>, Closeable {
     private CharBuffer buf;
 
     // Size of internal character buffer
-    private static final int BUFFER_SIZE = 1024; // change to 1024;
+    private static final int BUFFER_SIZE = 1024;
 
     // The index into the buffer currently held by the Scanner
     private int position;
 
     // Internal matcher used for finding delimiters
-    private Matcher matcher;
+    private final Matcher matcher;
 
     // Pattern used to delimit tokens
     private Pattern delimPattern;
@@ -371,7 +388,7 @@ public final class Scanner implements Iterator<String>, Closeable {
     private Locale locale = null;
 
     // A cache of the last few recently used Patterns
-    private PatternLRUCache patternCache = new PatternLRUCache(7);
+    private final PatternLRUCache patternCache = new PatternLRUCache(7);
 
     // A holder of the last IOException encountered
     private IOException lastException;
@@ -382,14 +399,14 @@ public final class Scanner implements Iterator<String>, Closeable {
     int modCount;
 
     // A pattern for java whitespace
-    private static Pattern WHITESPACE_PATTERN = Pattern.compile(
+    private static final Pattern WHITESPACE_PATTERN = Pattern.compile(
                                                 "\\p{javaWhitespace}+");
 
     // A pattern for any token
-    private static Pattern FIND_ANY_PATTERN = Pattern.compile("(?s).*");
+    private static final Pattern FIND_ANY_PATTERN = Pattern.compile("(?s).*");
 
     // A pattern for non-ASCII digits
-    private static Pattern NON_ASCII_DIGIT = Pattern.compile(
+    private static final Pattern NON_ASCII_DIGIT = Pattern.compile(
         "[\\p{javaDigit}&&[^0-9]]");
 
     // Fields and methods to support scanning primitive types
@@ -423,9 +440,9 @@ private static Pattern boolPattern() {
      * Fields and methods to match bytes, shorts, ints, and longs
      */
     private Pattern integerPattern;
-    private String digits = "0123456789abcdefghijklmnopqrstuvwxyz";
-    private String non0Digit = "[\\p{javaDigit}&&[^0]]";
-    private int SIMPLE_GROUP_INDEX = 5;
+    private static final String digits = "0123456789abcdefghijklmnopqrstuvwxyz";
+    private static final String non0Digit = "[\\p{javaDigit}&&[^0]]";
+    private static final int SIMPLE_GROUP_INDEX = 5;
     private String buildIntegerPatternString() {
         String radixDigits = digits.substring(0, radix);
         // \\p{javaDigit} is not guaranteed to be appropriate