gt:         if (ast != null) {
context: ////////////////////////////////////////////////////////////////////////////////
  // checkstyle: Checks Java source code for adherence to a set of rules.
  // Copyright (C) 2001-2016 the original author or authors.
  //
  // This library is free software; you can redistribute it and/or
  // modify it under the terms of the GNU Lesser General Public
  // License as published by the Free Software Foundation; either
  // version 2.1 of the License, or (at your option) any later version.
  //
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  // Lesser General Public License for more details.
  //
  // You should have received a copy of the GNU Lesser General Public
  // License along with this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ////////////////////////////////////////////////////////////////////////////////
  
  package com.puppycrawl.tools.checkstyle.checks;
  
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Locale;
  import java.util.Map;
  
  import org.apache.commons.beanutils.ConversionException;
  
  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
  import com.puppycrawl.tools.checkstyle.api.AuditEvent;
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  
  /**
   * Maintains a set of check suppressions from {@link SuppressWarnings}
   * annotations.
   * @author Trevor Robinson
   * @author St&eacute;phane Galland
   */
  public class SuppressWarningsHolder
      extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY = "suppress.warnings.invalid.target";
  
      /**
       * Optional prefix for warning suppressions that are only intended to be
       * recognized by checkstyle. For instance, to suppress {@code
       * FallThroughCheck} only in checkstyle (and not in javac), use the
       * suppression {@code "checkstyle:fallthrough"} or {@code "checkstyle:FallThrough"}.
       * To suppress the warning in both tools, just use {@code "fallthrough"}.
       */
      public static final String CHECKSTYLE_PREFIX = "checkstyle:";
  
      /** Java.lang namespace prefix, which is stripped from SuppressWarnings */
      private static final String JAVA_LANG_PREFIX = "java.lang.";
  
      /** Suffix to be removed from subclasses of Check. */
      private static final String CHECK_SUFFIX = "Check";
  
      /** Special warning id for matching all the warnings. */
      private static final String ALL_WARNING_MATCHING_ID = "all";
  
      /** A map from check source names to suppression aliases. */
      private static final Map<String, String> CHECK_ALIAS_MAP = new HashMap<>();
  
      /**
       * A thread-local holder for the list of suppression entries for the last
       * file parsed.
       */
      private static final ThreadLocal<List<Entry>> ENTRIES = new ThreadLocal<List<Entry>>() {
          @Override
          protected List<Entry> initialValue() {
              return new LinkedList<>();
          }
      };
  
      /**
       * Returns the default alias for the source name of a check, which is the
       * source name in lower case with any dotted prefix or "Check" suffix
       * removed.
       * @param sourceName the source name of the check (generally the class
       *        name)
       * @return the default alias for the given check
       */
      public static String getDefaultAlias(String sourceName) {
          final int startIndex = sourceName.lastIndexOf('.') + 1;
          int endIndex = sourceName.length();
          if (sourceName.endsWith(CHECK_SUFFIX)) {
              endIndex -= CHECK_SUFFIX.length();
          }
          return sourceName.substring(startIndex, endIndex).toLowerCase(Locale.ENGLISH);
      }
  
      /**
       * Returns the alias for the source name of a check. If an alias has been
       * explicitly registered via {@link #registerAlias(String, String)}, that
       * alias is returned; otherwise, the default alias is used.
       * @param sourceName the source name of the check (generally the class
       *        name)
       * @return the current alias for the given check
       */
      public static String getAlias(String sourceName) {
          String checkAlias = CHECK_ALIAS_MAP.get(sourceName);
          if (checkAlias == null) {
              checkAlias = getDefaultAlias(sourceName);
          }
          return checkAlias;
      }
  
      /**
       * Registers an alias for the source name of a check.
       * @param sourceName the source name of the check (generally the class
       *        name)
       * @param checkAlias the alias used in {@link SuppressWarnings} annotations
       */
      public static void registerAlias(String sourceName, String checkAlias) {
          CHECK_ALIAS_MAP.put(sourceName, checkAlias);
      }
  
      /**
       * Registers a list of source name aliases based on a comma-separated list
       * of {@code source=alias} items, such as {@code
       * com.puppycrawl.tools.checkstyle.checks.sizes.ParameterNumberCheck=
       * paramnum}.
       * @param aliasList the list of comma-separated alias assignments
       */
      public void setAliasList(String... aliasList) {
          for (String sourceAlias : aliasList) {
              final int index = sourceAlias.indexOf('=');
              if (index > 0) {
                  registerAlias(sourceAlias.substring(0, index), sourceAlias
                      .substring(index + 1));
              }
              else if (!sourceAlias.isEmpty()) {
                  throw new ConversionException(
                      "'=' expected in alias list item: " + sourceAlias);
              }
          }
      }
  
      /**
       * Checks for a suppression of a check with the given source name and
       * location in the last file processed.
       * @param event audit event.
       * @return whether the check with the given name is suppressed at the given
       *         source location
       */
      public static boolean isSuppressed(AuditEvent event) {
          final List<Entry> entries = ENTRIES.get();
          final String sourceName = event.getSourceName();
          final String checkAlias = getAlias(sourceName);
          final int line = event.getLine();
          final int column = event.getColumn();
          boolean suppressed = false;
          for (Entry entry : entries) {
              final boolean afterStart = isSuppressedAfterEventStart(line, column, entry);
              final boolean beforeEnd = isSuppressedBeforeEventEnd(line, column, entry);
              final boolean nameMatches =
                  ALL_WARNING_MATCHING_ID.equals(entry.getCheckName())
                      || entry.getCheckName().equalsIgnoreCase(checkAlias);
              final boolean idMatches = event.getModuleId() != null
                  && event.getModuleId().equals(entry.getCheckName());
              if (afterStart && beforeEnd && (nameMatches || idMatches)) {
                  suppressed = true;
              }
          }
          return suppressed;
      }
  
      /**
       * Checks whether suppression entry position is after the audit event occurrence position
       * in the source file.
       * @param line the line number in the source file where the event occurred.
       * @param column the column number in the source file where the event occurred.
       * @param entry suppression entry.
       * @return true if suppression entry position is after the audit event occurrence position
       *         in the source file.
       */
      private static boolean isSuppressedAfterEventStart(int line, int column, Entry entry) {
          return entry.getFirstLine() < line
              || entry.getFirstLine() == line
              && (column == 0 || entry.getFirstColumn() <= column);
      }
  
      /**
       * Checks whether suppression entry position is before the audit event occurrence position
       * in the source file.
       * @param line the line number in the source file where the event occurred.
       * @param column the column number in the source file where the event occurred.
       * @param entry suppression entry.
       * @return true if suppression entry position is before the audit event occurrence position
       *         in the source file.
       */
      private static boolean isSuppressedBeforeEventEnd(int line, int column, Entry entry) {
          return entry.getLastLine() > line
              || entry.getLastLine() == line && entry
                  .getLastColumn() >= column;
      }
  
      @Override
      public int[] getDefaultTokens() {
          return getAcceptableTokens();
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return new int[] {TokenTypes.ANNOTATION};
      }
  
      @Override
      public int[] getRequiredTokens() {
          return getAcceptableTokens();
      }
  
      @Override
      public void beginTree(DetailAST rootAST) {
          ENTRIES.get().clear();
      }
  
      @Override
      public void visitToken(DetailAST ast) {
          // check whether annotation is SuppressWarnings
          // expected children: AT ( IDENT | DOT ) LPAREN <values> RPAREN
          String identifier = getIdentifier(getNthChild(ast, 1));
          if (identifier.startsWith(JAVA_LANG_PREFIX)) {
              identifier = identifier.substring(JAVA_LANG_PREFIX.length());
          }
          if ("SuppressWarnings".equals(identifier)) {
  
              final List<String> values = getAllAnnotationValues(ast);
              if (!isAnnotationEmpty(values)) {
                  final DetailAST targetAST = getAnnotationTarget(ast);
  
                  if (targetAST == null) {
                      log(ast.getLineNo(), MSG_KEY);
                  }
                  else {
                      // get text range of target
                      final int firstLine = targetAST.getLineNo();
                      final int firstColumn = targetAST.getColumnNo();
                      final DetailAST nextAST = targetAST.getNextSibling();
                      final int lastLine;
                      final int lastColumn;
                      if (nextAST == null) {
                          lastLine = Integer.MAX_VALUE;
                          lastColumn = Integer.MAX_VALUE;
                      }
                      else {
                          lastLine = nextAST.getLineNo();
                          lastColumn = nextAST.getColumnNo() - 1;
                      }
  
                      // add suppression entries for listed checks
                      final List<Entry> entries = ENTRIES.get();
                      for (String value : values) {
                          String checkName = value;
                          // strip off the checkstyle-only prefix if present
                          checkName = removeCheckstylePrefixIfExists(checkName);
                          entries.add(new Entry(checkName, firstLine, firstColumn,
                                  lastLine, lastColumn));
                      }
                  }
              }
          }
      }
  
      /**
       * Method removes checkstyle prefix (checkstyle:) from check name if exists.
       *
       * @param checkName
       *            - name of the check
       * @return check name without prefix
       */
      private static String removeCheckstylePrefixIfExists(String checkName) {
          String result = checkName;
          if (checkName.startsWith(CHECKSTYLE_PREFIX)) {
              result = checkName.substring(CHECKSTYLE_PREFIX.length());
          }
          return result;
      }
  
      /**
       * Get all annotation values.
       * @param ast annotation token
       * @return list values
       */
      private static List<String> getAllAnnotationValues(DetailAST ast) {
          // get values of annotation
          List<String> values = null;
          final DetailAST lparenAST = ast.findFirstToken(TokenTypes.LPAREN);
          if (lparenAST != null) {
              final DetailAST nextAST = lparenAST.getNextSibling();
              final int nextType = nextAST.getType();
              switch (nextType) {
                  case TokenTypes.EXPR:
                  case TokenTypes.ANNOTATION_ARRAY_INIT:
                      values = getAnnotationValues(nextAST);
                      break;
  
                  case TokenTypes.ANNOTATION_MEMBER_VALUE_PAIR:
                      // expected children: IDENT ASSIGN ( EXPR |
                      // ANNOTATION_ARRAY_INIT )
                      values = getAnnotationValues(getNthChild(nextAST, 2));
                      break;
  
                  case TokenTypes.RPAREN:
                      // no value present (not valid Java)
                      break;
  
                  default:
                      // unknown annotation value type (new syntax?)
                      throw new IllegalArgumentException("Unexpected AST: " + nextAST);
              }
          }
          return values;
      }
  
      /**
       * Checks that annotation is empty.
       * @param values list of values in the annotation
       * @return whether annotation is empty or contains some values
       */
      private static boolean isAnnotationEmpty(List<String> values) {
          return values == null;
      }
  
      /**
       * Get target of annotation.
       * @param ast the AST node to get the child of
       * @return get target of annotation
       */
      private static DetailAST getAnnotationTarget(DetailAST ast) {
          final DetailAST targetAST;
          final DetailAST parentAST = ast.getParent();
          switch (parentAST.getType()) {
              case TokenTypes.MODIFIERS:
              case TokenTypes.ANNOTATIONS:
                  targetAST = getAcceptableParent(parentAST);
                  break;
              default:
                  // unexpected container type
                  throw new IllegalArgumentException("Unexpected container AST: " + parentAST);
          }
          return targetAST;
      }
  
      /**
       * Returns parent of given ast if parent has one of the following types:
       * ANNOTATION_DEF, PACKAGE_DEF, CLASS_DEF, ENUM_DEF, ENUM_CONSTANT_DEF, CTOR_DEF,
       * METHOD_DEF, PARAMETER_DEF, VARIABLE_DEF, ANNOTATION_FIELD_DEF, TYPE, LITERAL_NEW,
       * LITERAL_THROWS, TYPE_ARGUMENT, IMPLEMENTS_CLAUSE, DOT.
       * @param child an ast
       * @return returns ast - parent of given
       */
      private static DetailAST getAcceptableParent(DetailAST child) {
          final DetailAST result;
          final DetailAST parent = child.getParent();
          switch (parent.getType()) {
              case TokenTypes.ANNOTATION_DEF:
              case TokenTypes.PACKAGE_DEF:
              case TokenTypes.CLASS_DEF:
              case TokenTypes.INTERFACE_DEF:
              case TokenTypes.ENUM_DEF:
              case TokenTypes.ENUM_CONSTANT_DEF:
              case TokenTypes.CTOR_DEF:
              case TokenTypes.METHOD_DEF:
              case TokenTypes.PARAMETER_DEF:
              case TokenTypes.VARIABLE_DEF:
              case TokenTypes.ANNOTATION_FIELD_DEF:
              case TokenTypes.TYPE:
              case TokenTypes.LITERAL_NEW:
              case TokenTypes.LITERAL_THROWS:
              case TokenTypes.TYPE_ARGUMENT:
              case TokenTypes.IMPLEMENTS_CLAUSE:
              case TokenTypes.DOT:
                  result = parent;
                  break;
              default:
                  // it's possible case, but shouldn't be processed here
                  result = null;
          }
          return result;
      }
  
      /**
       * Returns the n'th child of an AST node.
       * @param ast the AST node to get the child of
       * @param index the index of the child to get
       * @return the n'th child of the given AST node, or {@code null} if none
       */
      private static DetailAST getNthChild(DetailAST ast, int index) {
          DetailAST child = ast.getFirstChild();
          for (int i = 0; i < index && child != null; ++i) {
              child = child.getNextSibling();
          }
          return child;
      }
  
      /**
       * Returns the Java identifier represented by an AST.
       * @param ast an AST node for an IDENT or DOT
       * @return the Java identifier represented by the given AST subtree
       * @throws IllegalArgumentException if the AST is invalid
       */
      private static String getIdentifier(DetailAST ast) {
  