Don't initialize an instance or static variable to its default value

src/main/config/checkstyle.xml

@@ -54,6 +54,7 @@ limitations under the License.
   </module>
 
   <module name="TreeWalker">
+    <module name="ExplicitInitializationCheck" />
     <module name="AvoidStarImport">
       <property name="excludes" value="org.junit.Assert,org.apache.commons.jexl3.parser"/>
     </module>

src/main/java/org/apache/commons/jexl3/JexlBuilder.java

@@ -100,25 +100,25 @@ public static void setDefaultPermissions(final JexlPermissions permissions) {
     protected static final int CACHE_THRESHOLD = 64;
 
     /** The JexlUberspect instance. */
-    private JexlUberspect uberspect = null;
+    private JexlUberspect uberspect;
 
     /** The {@link JexlUberspect} resolver strategy. */
-    private JexlUberspect.ResolverStrategy strategy = null;
+    private JexlUberspect.ResolverStrategy strategy;
 
     /** The set of permissions. */
     private JexlPermissions permissions;
 
     /** The sandbox. */
-    private JexlSandbox sandbox = null;
+    private JexlSandbox sandbox;
 
     /** The Log to which all JexlEngine messages will be logged. */
-    private Log logger = null;
+    private Log logger;
 
     /** Whether error messages will carry debugging information. */
-    private Boolean debug = null;
+    private Boolean debug;
 
     /** Whether interrupt throws JexlException.Cancel. */
-    private Boolean cancellable = null;
+    private Boolean cancellable;
 
     /** The options. */
     private final JexlOptions options = new JexlOptions();
@@ -127,7 +127,7 @@ public static void setDefaultPermissions(final JexlPermissions permissions) {
     private int collectMode = 1;
 
     /** The {@link JexlArithmetic} instance. */
-    private JexlArithmetic arithmetic = null;
+    private JexlArithmetic arithmetic;
 
     /** The cache size. */
     private int cache = -1;
@@ -142,10 +142,10 @@ public static void setDefaultPermissions(final JexlPermissions permissions) {
     private Charset charset = Charset.defaultCharset();
 
     /** The class loader. */
-    private ClassLoader loader = null;
+    private ClassLoader loader;
 
     /** The features. */
-    private JexlFeatures features = null;
+    private JexlFeatures features;
 
     /**
      * Default constructor.

src/main/java/org/apache/commons/jexl3/JexlOptions.java

@@ -65,7 +65,7 @@ public final class JexlOptions {
     /** Default mask .*/
     private static int DEFAULT = 1 /*<< CANCELLABLE*/ | 1 << STRICT | 1 << ANTISH | 1 << SAFE;
     /** The arithmetic math context. */
-    private MathContext mathContext = null;
+    private MathContext mathContext;
     /** The arithmetic math scale. */
     private int mathScale = Integer.MIN_VALUE;
     /** The arithmetic strict math flag. */

src/main/java/org/apache/commons/jexl3/internal/ArrayBuilder.java

@@ -55,15 +55,15 @@ protected static Class<?> unboxingClass(final Class<?> parm) {
     }
 
     /** The intended class array. */
-    protected Class<?> commonClass = null;
+    protected Class<?> commonClass;
     /** Whether the array stores numbers. */
     protected boolean isNumber = true;
     /** Whether we can try unboxing. */
     protected boolean unboxing = true;
     /** The untyped list of items being added. */
     protected final Object[] untyped;
     /** Number of added items. */
-    protected int added = 0;
+    protected int added;
     /** Extended? */
     protected final boolean extended;
 

src/main/java/org/apache/commons/jexl3/internal/Debugger.java

@@ -128,13 +128,13 @@ public class Debugger extends ParserVisitor implements JexlInfo.Detail {
     /** The builder to compose messages. */
     protected final StringBuilder builder = new StringBuilder();
     /** The cause of the issue to debug. */
-    protected JexlNode cause = null;
+    protected JexlNode cause;
     /** The starting character location offset of the cause in the builder. */
-    protected int start = 0;
+    protected int start;
     /** The ending character location offset of the cause in the builder. */
-    protected int end = 0;
+    protected int end;
     /** The indentation level. */
-    protected int indentLevel = 0;
+    protected int indentLevel;
     /** Perform indentation?. */
     protected int indent = 2;
     /** accept() relative depth. */
@@ -144,7 +144,7 @@ public class Debugger extends ParserVisitor implements JexlInfo.Detail {
     /** EOL. */
     protected String lf = "\n";
     /** Pragmas out. */
-    protected boolean outputPragmas = false;
+    protected boolean outputPragmas;
 
     /**
      * Creates a Debugger.

src/main/java/org/apache/commons/jexl3/internal/Engine.java

@@ -164,7 +164,7 @@ private UberspectHolder() {}
     /**
      * The default jxlt engine.
      */
-    protected volatile TemplateEngine jxlt = null;
+    protected volatile TemplateEngine jxlt;
     /**
      * Collect all or only dot references.
      */
@@ -824,7 +824,7 @@ protected static class VarCollector {
         /**
          * The node that started the collect.
          */
-        private JexlNode root = null;
+        private JexlNode root;
         /**
          * Whether constant array-access is considered equivalent to dot-access;
          * if so, > 1 means collect any constant (set,map,...) instead of just

src/main/java/org/apache/commons/jexl3/internal/Interpreter.java

@@ -129,11 +129,11 @@
  */
 public class Interpreter extends InterpreterBase {
     /** Frame height. */
-    protected int fp = 0;
+    protected int fp;
     /** Symbol values. */
     protected final Frame frame;
     /** Block micro-frames. */
-    protected LexicalFrame block = null;
+    protected LexicalFrame block;
 
     /**
      * The thread local interpreter.
@@ -2025,7 +2025,7 @@ public class AnnotatedCall implements Callable<Object> {
         /** The data. */
         private final Object data;
         /** Tracking whether we processed the annotation. */
-        private boolean processed = false;
+        private boolean processed;
 
         /**
          * Simple ctor.

src/main/java/org/apache/commons/jexl3/internal/InterpreterBase.java

@@ -833,15 +833,15 @@ protected class CallDispatcher {
         /** Whether solution is cacheable. */
         final boolean cacheable;
         /** Whether arguments have been narrowed.  */
-        boolean narrow = false;
+        boolean narrow;
         /** The method to call. */
-        JexlMethod vm = null;
+        JexlMethod vm;
         /** The method invocation target. */
-        Object target = null;
+        Object target;
         /** The actual arguments. */
-        Object[] argv = null;
+        Object[] argv;
         /** The cacheable funcall if any. */
-        Funcall funcall = null;
+        Funcall funcall;
 
         /**
          * Dispatcher ctor.

src/main/java/org/apache/commons/jexl3/internal/LexicalFrame.java

@@ -35,7 +35,7 @@ public class LexicalFrame extends LexicalScope {
     /**
      * The stack of values in the lexical frame.
      */
-    private Deque<Object> stack = null;
+    private Deque<Object> stack;
 
     /**
      * Lexical frame ctor.

src/main/java/org/apache/commons/jexl3/internal/LexicalScope.java

@@ -45,15 +45,15 @@ public class LexicalScope {
     /**
      * Number of symbols.
      */
-    protected int count = 0;
+    protected int count;
     /**
      * The mask of symbols in the scope.
      */
-    protected long symbols = 0L;
+    protected long symbols;
     /**
      * Symbols after bit 64 (aka symbol 32 when 2 bits per symbol).
      */
-    protected BitSet moreSymbols = null;
+    protected BitSet moreSymbols;
 
     /**
      * Create a scope.

src/main/java/org/apache/commons/jexl3/internal/Scope.java

@@ -61,15 +61,15 @@ public final class Scope {
      * Each parameter is associated to a symbol and is materialized as an offset in the stacked array used
      * during evaluation.
      */
-    private Map<String, Integer> namedVariables = null;
+    private Map<String, Integer> namedVariables;
     /**
      * The map of local captured variables to parent scope variables, ie closure.
      */
-    private Map<Integer, Integer> capturedVariables = null;
+    private Map<Integer, Integer> capturedVariables;
     /**
      * Let symbols.
      */
-    private LexicalScope lexicalVariables = null;
+    private LexicalScope lexicalVariables;
 
     /**
      * The empty string array.

src/main/java/org/apache/commons/jexl3/internal/SoftCache.java

@@ -46,7 +46,7 @@ public class SoftCache<K, V> {
     /**
      * The soft reference to the cache map.
      */
-    private SoftReference<Map<K, V>> ref = null;
+    private SoftReference<Map<K, V>> ref;
     /**
      * The cache r/w lock.
      */

src/main/java/org/apache/commons/jexl3/internal/introspection/IndexedType.java

@@ -37,11 +37,11 @@ public final class IndexedType implements JexlPropertyGet {
     /** The array of getter methods. */
     private final Method[] getters;
     /** Last get method used. */
-    private volatile Method get = null;
+    private volatile Method get;
     /** The array of setter methods. */
     private final Method[] setters;
     /** Last set method used. */
-    private volatile Method set = null;
+    private volatile Method set;
 
     /**
      * Attempts to find an indexed-property getter in an object.

src/main/java/org/apache/commons/jexl3/introspection/JexlSandbox.java

@@ -326,7 +326,7 @@ public String get(final String name) {
      */
     static class AllowSet extends Names {
         /** The map of controlled names and aliases. */
-        private Map<String, String> names = null;
+        private Map<String, String> names;
 
         @Override
         protected Names copy() {
@@ -370,7 +370,7 @@ public String get(final String name) {
      */
     static class BlockSet extends Names {
         /** The set of controlled names. */
-        private Set<String> names = null;
+        private Set<String> names;
 
         @Override
         protected Names copy() {

src/main/java/org/apache/commons/jexl3/parser/ASTAnnotation.java

@@ -24,7 +24,7 @@ public class ASTAnnotation extends JexlNode {
      *
      */
     private static final long serialVersionUID = 1L;
-    private String name = null;
+    private String name;
 
     ASTAnnotation(final int id) {
         super(id);

src/main/java/org/apache/commons/jexl3/parser/ASTArrayAccess.java

@@ -26,7 +26,7 @@ public class ASTArrayAccess extends JexlLexicalNode {
    * However, an expression like 'a?[b]?[c]?...?[b0]' with 64 terms is very unlikely
    * to occur in real life and a bad idea anyhow.
    */
-  private long safe = 0;
+  private long safe;
 
   public ASTArrayAccess(final int id) {
     super(id);

src/main/java/org/apache/commons/jexl3/parser/ASTIdentifier.java

@@ -24,9 +24,9 @@ public class ASTIdentifier extends JexlNode {
      *
      */
     private static final long serialVersionUID = 1L;
-    protected String name = null;
+    protected String name;
     protected int symbol = -1;
-    protected int flags = 0;
+    protected int flags;
 
     /** The redefined variable flag. */
     private static final int REDEFINED = 0;

src/main/java/org/apache/commons/jexl3/parser/ASTIdentifierAccess.java

@@ -25,8 +25,8 @@ public class ASTIdentifierAccess extends JexlNode {
      *
      */
     private static final long serialVersionUID = 1L;
-    private String name = null;
-    private Integer identifier = null;
+    private String name;
+    private Integer identifier;
 
     ASTIdentifierAccess(final int id) {
         super(id);

src/main/java/org/apache/commons/jexl3/parser/ASTJexlScript.java

@@ -29,7 +29,7 @@ public class ASTJexlScript extends JexlLexicalNode  {
     /** serial uid.*/
     private static final long serialVersionUID = 202112111533L;
     /** The pragmas. */
-    private Map<String, Object> pragmas = null;
+    private Map<String, Object> pragmas;
     /** Features. */
     private transient JexlFeatures features = null;
     /** The script scope. */

src/main/java/org/apache/commons/jexl3/parser/ASTJxltLiteral.java

@@ -22,7 +22,7 @@ public final class ASTJxltLiteral extends JexlNode {
     /** serial uid.*/
     private static final long serialVersionUID = 1L;
     /** The actual literal value. */
-    private String literal = null;
+    private String literal;
     /** The expression (parsed). */
     private transient JxltEngine.Expression jxltExpression = null;
 

src/main/java/org/apache/commons/jexl3/parser/ASTQualifiedIdentifier.java

@@ -24,7 +24,7 @@ public class ASTQualifiedIdentifier extends JexlNode {
      *
      */
     private static final long serialVersionUID = 1L;
-    protected String name = null;
+    protected String name;
 
     ASTQualifiedIdentifier(final int id) {
         super(id);

src/main/java/org/apache/commons/jexl3/parser/ASTRegexLiteral.java

@@ -26,7 +26,7 @@ public final class ASTRegexLiteral extends JexlNode implements JexlNode.Constant
     private static final long serialVersionUID = 1L;
     /** The actual literal value; the inherited 'value' member may host a cached getter. */
 
-    private Pattern literal = null;
+    private Pattern literal;
 
     ASTRegexLiteral(final int id) {
         super(id);

src/main/java/org/apache/commons/jexl3/parser/ASTStringLiteral.java

@@ -22,7 +22,7 @@ public final class ASTStringLiteral extends JexlNode implements JexlNode.Constan
      */
     private static final long serialVersionUID = 1L;
     /** The actual literal value; the inherited 'value' member may host a cached getter. */
-    private String literal = null;
+    private String literal;
 
     ASTStringLiteral(final int id) {
         super(id);

src/main/java/org/apache/commons/jexl3/parser/ExtensibleNode.java

@@ -25,9 +25,9 @@
  */
 public class ExtensibleNode extends JexlNode {
   /** Whether this array/set/map is constant or not. */
-  protected boolean constant = false;
+  protected boolean constant;
   /** Whether this array/set/map is extended or not. */
-  private boolean extended = false;
+  private boolean extended;
 
   public ExtensibleNode(final int id) {
     super(id);

src/main/java/org/apache/commons/jexl3/parser/JexlLexicalNode.java

@@ -25,7 +25,7 @@
 public abstract class JexlLexicalNode extends JexlNode implements JexlParser.LexicalUnit {
     private static final long serialVersionUID = 1L;
     /** The local lexical scope, local information about let/const. */
-    private LexicalScope lexicalScope = null;
+    private LexicalScope lexicalScope;
 
     public JexlLexicalNode(final int id) {
         super(id);