Mark fields final where possible. #1538

src/main/java/com/puppycrawl/tools/checkstyle/PropertyCacheFile.java

@@ -73,10 +73,10 @@ final class PropertyCacheFile {
     private final Properties details = new Properties();
 
     /** configuration object **/
-    private Configuration config;
+    private final Configuration config;
 
     /** file name of cache **/
-    private String fileName;
+    private final String fileName;
 
     /**
      * Creates a new <code>PropertyCacheFile</code> instance.

src/main/java/com/puppycrawl/tools/checkstyle/XMLLogger.java

@@ -53,7 +53,7 @@ public class XMLLogger
                                               "quot", };
 
     /** close output stream in auditFinished */
-    private boolean closeStream;
+    private final boolean closeStream;
 
     /** helper writer that allows easy encoding and printing */
     private PrintWriter writer;

src/main/java/com/puppycrawl/tools/checkstyle/api/SeverityLevelCounter.java

@@ -27,7 +27,7 @@ package com.puppycrawl.tools.checkstyle.api;
  */
 public final class SeverityLevelCounter implements AuditListener {
     /** The severity level to watch out for. */
-    private SeverityLevel level;
+    private final SeverityLevel level;
 
     /** Keeps track of the number of counted events. */
     private int count;

src/main/java/com/puppycrawl/tools/checkstyle/checks/AvoidEscapedUnicodeCharactersCheck.java

@@ -107,25 +107,25 @@ import com.puppycrawl.tools.checkstyle.api.TokenTypes;
 public class AvoidEscapedUnicodeCharactersCheck
     extends Check {
     /** Regular expression for Unicode chars */
-    private static Pattern sUnicodeRegexp = Pattern.compile("\\\\u[a-fA-F0-9]{4}");
+    private static final Pattern UNICODE_REGEXP = Pattern.compile("\\\\u[a-fA-F0-9]{4}");
 
     /** Regular expression Unicode control characters */
-    private static Pattern sUnicodeControl = Pattern.compile("\\\\(u|U)"
+    private static final Pattern UNICODE_CONTROL = Pattern.compile("\\\\(u|U)"
             + "(00[0-1][0-1A-Fa-f]|00[8-9][0-9A-Fa-f]|034(f|F)|070(f|F)"
             + "|180(e|E)|200[b-fB-F]|202[b-eB-E]|206[0-4a-fA-F]"
             + "|[fF]{3}[9a-bA-B]|[fF][eE][fF]{2})");
 
     /** Regular expression for trail comment */
-    private static Pattern sCommentRegexp = Pattern.compile(";[ ]*//+"
+    private static final Pattern COMMENT_REGEXP = Pattern.compile(";[ ]*//+"
             + "[a-zA-Z0-9 ]*|;[ ]*/[*]{1}+[a-zA-Z0-9 ]*");
 
     /** Regular expression for all escaped chars */
-    private static Pattern sAllEscapedChars =
+    private static final Pattern ALL_ESCAPED_CHARS =
             Pattern.compile("^((\\\\u)[a-fA-F0-9]{4}"
                     + "||\\\\b|\\\\t|\\\\n|\\\\f|\\\\r|\\\\|\\\"|\\\')+$");
 
     /** Regular expression for non-printable unicode chars */
-    private static Pattern sNonPrintableChars = Pattern.compile("\\\\u1680|\\\\u2028"
+    private static final Pattern NON_PRINTABLE_CHARS = Pattern.compile("\\\\u1680|\\\\u2028"
             + "|\\\\u2029|\\\\u205(f|F)|\\\\u3000|\\\\u2007|\\\\u2000|\\\\u200(a|A)"
             + "|\\\\u007(F|f)|\\\\u009(f|F)|\\\\u(f|F){4}|\\\\u007(F|f)|\\\\u00(a|A)(d|D)"
             + "|\\\\u0600|\\\\u061(c|C)|\\\\u06(d|D){2}|\\\\u070(f|F)|\\\\u1680|\\\\u180(e|E)"
@@ -208,9 +208,9 @@ public class AvoidEscapedUnicodeCharactersCheck
         if (hasUnicodeChar(literal) && !(allowByTailComment && hasTrailComment(ast)
                 || isAllCharactersEscaped(literal)
                 || allowEscapesForControlCharacters
-                        && isOnlyUnicodeValidChars(literal, sUnicodeControl)
+                        && isOnlyUnicodeValidChars(literal, UNICODE_CONTROL)
                 || allowNonPrintableEscapes
-                        && isOnlyUnicodeValidChars(literal, sNonPrintableChars))) {
+                        && isOnlyUnicodeValidChars(literal, NON_PRINTABLE_CHARS))) {
             log(ast.getLineNo(), "forbid.escaped.unicode.char");
         }
     }
@@ -221,7 +221,7 @@ public class AvoidEscapedUnicodeCharactersCheck
      * @return true if literal has Unicode chars.
      */
     private static boolean hasUnicodeChar(String literal) {
-        return sUnicodeRegexp.matcher(literal).find();
+        return UNICODE_REGEXP.matcher(literal).find();
     }
 
     /**
@@ -232,7 +232,7 @@ public class AvoidEscapedUnicodeCharactersCheck
      */
     private static boolean isOnlyUnicodeValidChars(String literal, Pattern pattern) {
         final int unicodeMatchesCounter =
-                countMatches(sUnicodeRegexp, literal);
+                countMatches(UNICODE_REGEXP, literal);
         final int unicodeValidMatchesCouter =
                 countMatches(pattern, literal);
         return unicodeMatchesCounter - unicodeValidMatchesCouter == 0;
@@ -264,7 +264,7 @@ public class AvoidEscapedUnicodeCharactersCheck
             final int lineNo = semi.getLineNo();
             final String currentLine = getLine(lineNo - 1);
 
-            if (sCommentRegexp.matcher(currentLine).find()) {
+            if (COMMENT_REGEXP.matcher(currentLine).find()) {
                 result = true;
             }
         }
@@ -325,7 +325,7 @@ public class AvoidEscapedUnicodeCharactersCheck
      */
     private boolean isAllCharactersEscaped(String literal) {
         return allowIfAllCharactersEscaped
-                && sAllEscapedChars.matcher(literal.substring(1,
+                && ALL_ESCAPED_CHARS.matcher(literal.substring(1,
                         literal.length() - 1)).find();
     }
 }

src/main/java/com/puppycrawl/tools/checkstyle/checks/design/HideUtilityClassConstructorCheck.java

@@ -107,7 +107,7 @@ public class HideUtilityClassConstructorCheck extends Check {
      */
     private static class Details {
         /** class ast */
-        private DetailAST ast;
+        private final DetailAST ast;
         /** result of details gathering */
         private boolean hasMethodOrField;
         /** result of details gathering */

src/main/java/com/puppycrawl/tools/checkstyle/checks/design/OneTopLevelClassCheck.java

@@ -98,7 +98,7 @@ public class OneTopLevelClassCheck extends Check {
     private boolean publicTypeFound;
 
     /** Mapping between type names and line numbers of the type declarations.*/
-    private SortedMap<Integer, String> lineNumberTypeMap = new TreeMap<>();
+    private final SortedMap<Integer, String> lineNumberTypeMap = new TreeMap<>();
 
     @Override
     public int[] getDefaultTokens() {

src/main/java/com/puppycrawl/tools/checkstyle/checks/design/VisibilityModifierCheck.java

@@ -292,7 +292,7 @@ public class VisibilityModifierCheck
             new ArrayList<>(DEFAULT_IGNORE_ANNOTATIONS);
 
     /** List of ignore annotations short names. */
-    private List<String> ignoreAnnotationShortNames =
+    private final List<String> ignoreAnnotationShortNames =
             getClassShortNames(DEFAULT_IGNORE_ANNOTATIONS);
 
     /** Allows immutable fields to be declared as public. */

src/main/java/com/puppycrawl/tools/checkstyle/checks/imports/CustomImportOrderCheck.java

@@ -324,7 +324,7 @@ public class CustomImportOrderCheck extends Check {
     private int samePackageMatchingDepth = 2;
 
     /** Contains objects with import attributes */
-    private List<ImportDetails> importToGroupList = new ArrayList<>();
+    private final List<ImportDetails> importToGroupList = new ArrayList<>();
 
     /**
      * Sets standardRegExp specified by user.

src/main/java/com/puppycrawl/tools/checkstyle/checks/indentation/LineWrappingHandler.java

@@ -47,22 +47,22 @@ public class LineWrappingHandler {
     /**
      * Root node for current expression.
      */
-    private DetailAST firstNode;
+    private final DetailAST firstNode;
 
     /**
      * Last node for current expression.
      */
-    private DetailAST lastNode;
+    private final DetailAST lastNode;
 
     /**
      * User's value of line wrapping indentation.
      */
-    private int indentLevel;
+    private final int indentLevel;
 
     /**
      * Force strict condition in line wrapping case.
      */
-    private boolean forceStrictCondition;
+    private final boolean forceStrictCondition;
 
     /**
      * Sets values of class field, finds last node and calculates indentation level.

src/main/java/com/puppycrawl/tools/checkstyle/checks/indentation/SynchronizedHandler.java

@@ -32,7 +32,7 @@ public class SynchronizedHandler extends BlockParentHandler {
     /**
      * Determine that "synchronized" token used as modifier of method
      */
-    private boolean methodModifier;
+    private final boolean methodModifier;
 
     /**
      * Construct an instance of this handler with the given indentation check,

src/main/java/com/puppycrawl/tools/checkstyle/checks/javadoc/AbstractJavadocCheck.java

@@ -636,17 +636,17 @@ public abstract class AbstractJavadocCheck extends Check {
         /**
          * Line number where parse error occurred.
          */
-        private int lineNumber;
+        private final int lineNumber;
 
         /**
          * Key for error message.
          */
-        private String messageKey;
+        private final String messageKey;
 
         /**
          * Error message arguments.
          */
-        private Object[] messageArguments;
+        private final Object[] messageArguments;
 
         /**
          * Initializes parse error message.

src/main/java/com/puppycrawl/tools/checkstyle/checks/javadoc/JavadocTag.java

@@ -29,7 +29,7 @@ public class JavadocTag {
     /** the line number of the tag **/
     private final int lineNo;
     /** the column number of the tag **/
-    private int columnNo;
+    private final int columnNo;
     /** an optional first argument. For example the parameter name. **/
     private final String arg1;
     /** the JavadocTagInfo representing this tag **/

src/main/java/com/puppycrawl/tools/checkstyle/checks/naming/LocalVariableNameCheck.java

@@ -74,7 +74,7 @@ import com.puppycrawl.tools.checkstyle.api.TokenTypes;
 public class LocalVariableNameCheck
     extends AbstractNameCheck {
     /** Regexp for one-char loop variables. */
-    private static Pattern sSingleChar = Pattern.compile("^[a-z]$");
+    private static final Pattern SINGLE_CHAR = Pattern.compile("^[a-z]$");
 
     /**
      * Allow one character name for initialization expression in FOR loop.
@@ -111,7 +111,7 @@ public class LocalVariableNameCheck
         if (allowOneCharVarInForLoop && isForLoopVariable(ast)) {
             final String variableName =
                     ast.findFirstToken(TokenTypes.IDENT).getText();
-            return !sSingleChar.matcher(variableName).find();
+            return !SINGLE_CHAR.matcher(variableName).find();
         }
         final DetailAST modifiersAST =
             ast.findFirstToken(TokenTypes.MODIFIERS);

src/main/java/com/puppycrawl/tools/checkstyle/checks/regexp/RegexpMultilineCheck.java

@@ -33,7 +33,7 @@ import com.puppycrawl.tools.checkstyle.api.FileText;
  */
 public class RegexpMultilineCheck extends AbstractFileSetCheck {
     /** The detection options to use. */
-    private DetectorOptions options = new DetectorOptions(Pattern.MULTILINE,
+    private final DetectorOptions options = new DetectorOptions(Pattern.MULTILINE,
             this);
     /** The detector to use. */
     private MultilineDetector detector;

src/main/java/com/puppycrawl/tools/checkstyle/checks/regexp/RegexpSinglelineCheck.java

@@ -30,7 +30,7 @@ import com.puppycrawl.tools.checkstyle.api.AbstractFileSetCheck;
  */
 public class RegexpSinglelineCheck extends AbstractFileSetCheck {
     /** The detection options to use. */
-    private DetectorOptions options = new DetectorOptions(0, this);
+    private final DetectorOptions options = new DetectorOptions(0, this);
     /** The detector to use. */
     private SinglelineDetector detector;
 

src/main/java/com/puppycrawl/tools/checkstyle/checks/regexp/RegexpSinglelineJavaCheck.java

@@ -31,7 +31,7 @@ import com.puppycrawl.tools.checkstyle.api.DetailAST;
  */
 public class RegexpSinglelineJavaCheck extends Check {
     /** The detection options to use. */
-    private DetectorOptions options = new DetectorOptions(0, this);
+    private final DetectorOptions options = new DetectorOptions(0, this);
     /** The detector to use. */
     private SinglelineDetector detector;
     /** The suppressor to use. */