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Checkstyle is a development tool to help programmers write Java code
that adheres to a coding standard
////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2022 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.coding;
import java.util.Objects;
import com.puppycrawl.tools.checkstyle.StatelessCheck;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
/**
*
* Check that the {@code default} is after all the cases in a {@code switch} statement.
*
*
* Rationale: Java allows {@code default} anywhere within the
* {@code switch} statement. But it is more readable if it comes after the last {@code case}.
*
*
* -
* Property {@code skipIfLastAndSharedWithCase} - Control whether to allow {@code default}
* along with {@code case} if they are not last.
* Type is {@code boolean}.
* Default value is {@code false}.
*
*
*
* To configure the check:
*
*
* <module name="DefaultComesLast"/>
*
* Example:
*
* switch (i) {
* case 1:
* break;
* case 2:
* break;
* default: // OK
* break;
* }
*
* switch (i) {
* case 1:
* break;
* case 2:
* break; // OK, no default
* }
*
* switch (i) {
* case 1:
* break;
* default: // violation, 'default' before 'case'
* break;
* case 2:
* break;
* }
*
* switch (i) {
* case 1:
* default: // violation, 'default' before 'case'
* break;
* case 2:
* break;
* }
*
* To configure the check to allow default label to be not last if it is shared with case:
*
*
* <module name="DefaultComesLast">
* <property name="skipIfLastAndSharedWithCase" value="true"/>
* </module>
*
* Example:
*
* switch (i) {
* case 1:
* break;
* case 2:
* default: // OK
* break;
* case 3:
* break;
* }
*
* switch (i) {
* case 1:
* break;
* default: // violation
* case 2:
* break;
* }
*
* // Switch rules are not subject to fall through, so this is still a violation:
* switch (i) {
* case 1 -> x = 9;
* default -> x = 10; // violation
* case 2 -> x = 32;
* }
*
*
* Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
*
*
* Violation Message Keys:
*
*
* -
* {@code default.comes.last}
*
* -
* {@code default.comes.last.in.casegroup}
*
*
*
* @since 3.4
*/
@StatelessCheck
public class DefaultComesLastCheck extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY = "default.comes.last";
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY_SKIP_IF_LAST_AND_SHARED_WITH_CASE =
"default.comes.last.in.casegroup";
/** Control whether to allow {@code default} along with {@code case} if they are not last. */
private boolean skipIfLastAndSharedWithCase;
@Override
public int[] getAcceptableTokens() {
return getRequiredTokens();
}
@Override
public int[] getDefaultTokens() {
return getRequiredTokens();
}
@Override
public int[] getRequiredTokens() {
return new int[] {
TokenTypes.LITERAL_DEFAULT,
};
}
/**
* Setter to control whether to allow {@code default} along with
* {@code case} if they are not last.
*
* @param newValue whether to ignore checking.
*/
public void setSkipIfLastAndSharedWithCase(boolean newValue) {
skipIfLastAndSharedWithCase = newValue;
}
@Override
public void visitToken(DetailAST ast) {
final DetailAST defaultGroupAST = ast.getParent();
// Switch rules are not subject to fall through.
final boolean isSwitchRule = defaultGroupAST.getType() == TokenTypes.SWITCH_RULE;
if (skipIfLastAndSharedWithCase && !isSwitchRule) {
if (Objects.nonNull(findNextSibling(ast, TokenTypes.LITERAL_CASE))) {
log(ast, MSG_KEY_SKIP_IF_LAST_AND_SHARED_WITH_CASE);
}
else if (ast.getPreviousSibling() == null
&& Objects.nonNull(findNextSibling(defaultGroupAST,
TokenTypes.CASE_GROUP))) {
log(ast, MSG_KEY);
}
}
else if (Objects.nonNull(findNextSibling(defaultGroupAST,
TokenTypes.CASE_GROUP))
|| Objects.nonNull(findNextSibling(defaultGroupAST,
TokenTypes.SWITCH_RULE))) {
log(ast, MSG_KEY);
}
}
/**
* Return token type only if passed tokenType in argument is found or returns -1.
*
* @param ast root node.
* @param tokenType tokentype to be processed.
* @return token if desired token is found or else null.
*/
private static DetailAST findNextSibling(DetailAST ast, int tokenType) {
DetailAST token = null;
DetailAST node = ast.getNextSibling();
while (node != null) {
if (node.getType() == tokenType) {
token = node;
break;
}
node = node.getNextSibling();
}
return token;
}
}