////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2015 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.modifier;

import java.util.ArrayList;
import java.util.List;

import com.puppycrawl.tools.checkstyle.api.Check;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;


/**
 * Checks for redundant modifiers in interface and annotation definitions.
 * Also checks for redundant final modifiers on methods of final classes
 * and redundant enum constructor modifier.
 *
 * @author lkuehne
 * @author <a href="mailto:piotr.listkiewicz@gmail.com">liscju</a>
 */
public class RedundantModifierCheck
    extends Check {

    /**
     * A key is pointing to the warning message text in "messages.properties"
     * file.
     */
    public static final String MSG_KEY = "redundantModifier";

    /**
     * An array of tokens for interface modifiers.
     */
    private static final int[] TOKENS_FOR_INTERFACE_MODIFIERS = new int[] {
        TokenTypes.LITERAL_STATIC,
        TokenTypes.ABSTRACT,
    };

    @Override
    public int[] getDefaultTokens() {
        return getAcceptableTokens();
    }

    @Override
    public int[] getRequiredTokens() {
        return new int[] {};
    }

    @Override
    public int[] getAcceptableTokens() {
        return new int[] {
            TokenTypes.METHOD_DEF,
            TokenTypes.VARIABLE_DEF,
            TokenTypes.ANNOTATION_FIELD_DEF,
            TokenTypes.INTERFACE_DEF,
            TokenTypes.CTOR_DEF,
            TokenTypes.CLASS_DEF,
            TokenTypes.ENUM_DEF,
        };
    }

    @Override
    public void visitToken(DetailAST ast) {
        if (TokenTypes.INTERFACE_DEF == ast.getType()) {
            checkInterfaceModifiers(ast);
        }
        else if (TokenTypes.CTOR_DEF == ast.getType()
                && isEnumMember(ast)) {
            checkEnumConstructorModifiers(ast);
        }
        else if (isInterfaceOrAnnotationMember(ast)) {
            processInterfaceOrAnnotation(ast);
        }
        else if (ast.getType() == TokenTypes.METHOD_DEF) {
            processMethods(ast);
        }
    }

    /**
     * Checks if interface has proper modifiers
     * @param ast interface to check
     */
    private void checkInterfaceModifiers(DetailAST ast) {
        final DetailAST modifiers =
            ast.findFirstToken(TokenTypes.MODIFIERS);

        for (final int tokenType : TOKENS_FOR_INTERFACE_MODIFIERS) {
            final DetailAST modifier =
                    modifiers.findFirstToken(tokenType);
            if (modifier != null) {
                log(modifier.getLineNo(), modifier.getColumnNo(),
                        MSG_KEY, modifier.getText());
            }
        }
    }

    /**
     * Check if enum constructor has proper modifiers
     * @param ast constructor of enum
     */
    private void checkEnumConstructorModifiers(DetailAST ast) {
        final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
        final DetailAST modifier = modifiers.getFirstChild();
        if (modifier != null) {
            log(modifier.getLineNo(), modifier.getColumnNo(),
                    MSG_KEY, modifier.getText());
        }
    }

    /**
     * do validation of interface of annotation
     * @param ast token AST
     */
    private void processInterfaceOrAnnotation(DetailAST ast) {
        final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
        DetailAST modifier = modifiers.getFirstChild();
        while (modifier != null) {

            // javac does not allow final or static in interface methods
            // order annotation fields hence no need to check that this
            // is not a method or annotation field

            final int type = modifier.getType();
            if (type == TokenTypes.LITERAL_PUBLIC
                || type == TokenTypes.LITERAL_STATIC
                        && ast.getType() != TokenTypes.METHOD_DEF
                || type == TokenTypes.ABSTRACT
                || type == TokenTypes.FINAL) {
                log(modifier.getLineNo(), modifier.getColumnNo(),
                        MSG_KEY, modifier.getText());
                break;
            }

            modifier = modifier.getNextSibling();
        }
    }

    /**
     * process validation ofMethods
     * @param ast method AST
     */
    private void processMethods(DetailAST ast) {
        final DetailAST modifiers =
                        ast.findFirstToken(TokenTypes.MODIFIERS);
        // private method?
        boolean checkFinal =
            modifiers.branchContains(TokenTypes.LITERAL_PRIVATE);
        // declared in a final class?
        DetailAST parent = ast.getParent();
        while (parent != null) {
            if (parent.getType() == TokenTypes.CLASS_DEF) {
                final DetailAST classModifiers =
                    parent.findFirstToken(TokenTypes.MODIFIERS);
                checkFinal |=
                    classModifiers.branchContains(TokenTypes.FINAL);
                break;
            }
            parent = parent.getParent();
        }
        if (checkFinal && !isAnnotatedWithSafeVarargs(ast)) {
            DetailAST modifier = modifiers.getFirstChild();
            while (modifier != null) {
                final int type = modifier.getType();
                if (type == TokenTypes.FINAL) {
                    log(modifier.getLineNo(), modifier.getColumnNo(),
                            MSG_KEY, modifier.getText());
                    break;
                }
                modifier = modifier.getNextSibling();
            }
        }
    }

    /**
     * Checks if current AST node is member of Enum
     * @param ast AST node
     * @return true if it is an enum member
     */
    private boolean isEnumMember(DetailAST ast) {
        final DetailAST parentTypeDef = ast.getParent().getParent();
        return parentTypeDef.getType() == TokenTypes.ENUM_DEF;
    }

    /**
     * Checks if current AST node is member of Interface or Annotation, not of their subnodes.
     * @param ast AST node
     * @return true or false
     */
    private static boolean isInterfaceOrAnnotationMember(DetailAST ast) {
        final DetailAST parentTypeDef =
                ast.getParent() != null ? ast.getParent().getParent() : null;
        return parentTypeDef != null
                && (parentTypeDef.getType() == TokenTypes.INTERFACE_DEF
                    || parentTypeDef.getType() == TokenTypes.ANNOTATION_DEF);
    }

    /**
     * Checks if method definition is annotated with
     * <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/SafeVarargs.html">
     * SafeVarargs</a> annotation
     * @param methodDef method definition node
     * @return true or false
     */
    private static boolean isAnnotatedWithSafeVarargs(DetailAST methodDef) {
        boolean result = false;
        final List<DetailAST> methodAnnotationsList = getMethodAnnotationsList(methodDef);
        for (DetailAST annotationNode : methodAnnotationsList) {
            if ("SafeVarargs".equals(annotationNode.getLastChild().getText())) {
                result = true;
                break;
            }
        }
        return result;
    }

    /**
     * Gets the list of annotations on method definition
     * @param methodDef method definition node
     * @return List of annotations
     */
    private static List<DetailAST> getMethodAnnotationsList(DetailAST methodDef) {
        final List<DetailAST> annotationsList = new ArrayList<>();
        final DetailAST modifiers = methodDef.findFirstToken(TokenTypes.MODIFIERS);
        DetailAST modifier = modifiers.getFirstChild();
        while (modifier != null) {
            if (modifier.getType() == TokenTypes.ANNOTATION) {
                annotationsList.add(modifier);
            }
            modifier = modifier.getNextSibling();
        }
        return annotationsList;
    }
}

@@ -6744,16 +6744,23 @@
 private 
+static 
 boolean 

Make method "static". #46