com.puppycrawl.tools.checkstyle.checks.blocks

Class EmptyBlockCheck

java.lang.Object

com.puppycrawl.tools.checkstyle.api.AutomaticBean

com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter

com.puppycrawl.tools.checkstyle.api.AbstractCheck

com.puppycrawl.tools.checkstyle.checks.blocks.EmptyBlockCheck

All Implemented Interfaces:

Configurable, Contextualizable

public class EmptyBlockCheck
extends AbstractCheck

Checks for empty blocks. This check does not validate sequential blocks.

Sequential blocks won't be checked. Also, no violations for fallthrough:

 switch (a) {
   case 1:                          // no violation
   case 2:                          // no violation
   case 3: someMethod(); { }        // no violation
   default: break;
 }
 

NOTE: This check processes LITERAL_CASE and LITERAL_DEFAULT separately. Verification empty block is done for single most nearest case or default.

• Property option - specify the policy on block contents. Type is com.puppycrawl.tools.checkstyle.checks.blocks.BlockOption. Default value is statement.
• Property tokens - tokens to check Type is java.lang.String[]. Validation type is tokenSet. Default value is: LITERAL_WHILE, LITERAL_TRY, LITERAL_FINALLY, LITERAL_DO, LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, INSTANCE_INIT, STATIC_INIT, LITERAL_SWITCH, LITERAL_SYNCHRONIZED.

To configure the check:

 <module name="EmptyBlock"/>
 

Example:

 public class Test {
   private void emptyLoop() {
     for (int i = 0; i < 10; i++) { // violation
     }

     try { // violation

     } catch (Exception e) {
       // ignored
     }
   }
 }
 

To configure the check for the text policy and only try blocks:

 <module name="EmptyBlock">
   <property name="option" value="text"/>
   <property name="tokens" value="LITERAL_TRY"/>
 </module>
 

Example:

 public class Test {
   private void emptyLoop() {
     for (int i = 0; i < 10; i++) {
       // ignored
     }

     // violation on next line
     try {

     } catch (Exception e) {
       // ignored
     }
   }
 }
 

To configure the check for default in switch block:

 <module name="EmptyBlock">
   <property name="tokens" value="LITERAL_DEFAULT"/>
 </module>
 

Example:

 public class Test {
   private void test(int a) {
     switch (a) {
       case 1: someMethod();
       default: // OK, as there is no block
     }
     switch (a) {
       case 1: someMethod();
       default: {} // violation
     }
   }
 }
 

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

• block.empty
• block.noStatement

Since:

3.0

Nested Class Summary

Nested classes/interfaces inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean

AutomaticBean.OutputStreamOptions

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	MSG_KEY_BLOCK_EMPTY A key is pointing to the warning message text in "messages.properties" file.
static java.lang.String	MSG_KEY_BLOCK_NO_STATEMENT A key is pointing to the warning message text in "messages.properties" file.
private BlockOption	option Specify the policy on block contents.

Constructor Summary

Constructors

Constructor and Description
EmptyBlockCheck()

Method Summary

Modifier and Type	Method and Description
private static boolean	checkIsAllLinesAreWhitespace(java.lang.String[] lines, int lineFrom, int lineTo) Checks is all lines in array contain whitespaces only.
private static DetailAST	findLeftCurly(DetailAST ast) Calculates the left curly corresponding to the block to be checked.
int[]	getAcceptableTokens() The configurable token set.
int[]	getDefaultTokens() Returns the default token a check is interested in.
int[]	getRequiredTokens() The tokens that this check must be registered for.
private boolean	hasText(DetailAST slistAST) Checks if SLIST token contains any text.
void	setOption(java.lang.String optionStr) Setter to specify the policy on block contents.
void	visitToken(DetailAST ast) Called to process a token.

Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractCheck

beginTree, clearViolations, destroy, finishTree, getFileContents, getLine, getLineCodePoints, getLines, getTabWidth, getTokenNames, getViolations, init, isCommentNodesRequired, leaveToken, log, log, log, setFileContents, setTabWidth, setTokens

Methods inherited from class com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter

finishLocalSetup, getCustomMessages, getId, getMessageBundle, getSeverity, getSeverityLevel, setId, setSeverity

Methods inherited from class com.puppycrawl.tools.checkstyle.api.AutomaticBean

configure, contextualize, getConfiguration, setupChild

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MSG_KEY_BLOCK_NO_STATEMENT

public static final java.lang.String MSG_KEY_BLOCK_NO_STATEMENT

A key is pointing to the warning message text in "messages.properties" file.

See Also:

Constant Field Values

MSG_KEY_BLOCK_EMPTY

public static final java.lang.String MSG_KEY_BLOCK_EMPTY

A key is pointing to the warning message text in "messages.properties" file.

See Also:

Constant Field Values

option

private BlockOption option

Specify the policy on block contents.

Constructor Detail

EmptyBlockCheck

public EmptyBlockCheck()

Method Detail

setOption

public void setOption(java.lang.String optionStr)

Setter to specify the policy on block contents.

Parameters:

optionStr - string to decode option from

Throws:

java.lang.IllegalArgumentException - if unable to decode

getDefaultTokens

public int[] getDefaultTokens()

Description copied from class: AbstractCheck

Returns the default token a check is interested in. Only used if the configuration for a check does not define the tokens.

Specified by:

getDefaultTokens in class AbstractCheck

Returns:

the default tokens

See Also:

TokenTypes

getAcceptableTokens

public int[] getAcceptableTokens()

Description copied from class: AbstractCheck

The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.

Specified by:

getAcceptableTokens in class AbstractCheck

Returns:

the token set this check is designed for.

See Also:

TokenTypes

getRequiredTokens

public int[] getRequiredTokens()

Description copied from class: AbstractCheck

The tokens that this check must be registered for.

Specified by:

getRequiredTokens in class AbstractCheck

Returns:

the token set this must be registered for.

See Also:

TokenTypes

visitToken

public void visitToken(DetailAST ast)

Description copied from class: AbstractCheck

Called to process a token.

Overrides:

visitToken in class AbstractCheck

Parameters:

ast - the token to process

hasText

private boolean hasText(DetailAST slistAST)

Checks if SLIST token contains any text.

Parameters:

slistAST - a DetailAST value

Returns:

whether the SLIST token contains any text.

checkIsAllLinesAreWhitespace

private static boolean checkIsAllLinesAreWhitespace(java.lang.String[] lines,
                                                    int lineFrom,
                                                    int lineTo)

Checks is all lines in array contain whitespaces only.

Parameters:

lines - array of lines

lineFrom - check from this line number

lineTo - check to this line numbers

Returns:

true if lines contain only whitespaces

findLeftCurly

private static DetailAST findLeftCurly(DetailAST ast)

Calculates the left curly corresponding to the block to be checked.

Parameters:

ast - a DetailAST value

Returns:

the left curly corresponding to the block to be checked