com.puppycrawl.tools.checkstyle.checks.coding

Class IllegalInstantiationCheck

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.coding.IllegalInstantiationCheck

All Implemented Interfaces:

Configurable, Contextualizable

public class IllegalInstantiationCheck
extends AbstractCheck

Checks for illegal instantiations where a factory method is preferred.

Rationale: Depending on the project, for some classes it might be preferable to create instances through factory methods rather than calling the constructor.

A simple example is the java.lang.Boolean class. For performance reasons, it is preferable to use the predefined constants TRUE and FALSE. Constructor invocations should be replaced by calls to Boolean.valueOf().

Some extremely performance sensitive projects may require the use of factory methods for other classes as well, to enforce the usage of number caches or object pools.

There is a limitation that it is currently not possible to specify array classes.

• Property classes - Specify fully qualified class names that should not be instantiated. Type is java.lang.String[]. Default value is "".
• Property tokens - tokens to check Type is java.lang.String[]. Validation type is tokenSet. Default value is: CLASS_DEF.

To configure the check:

 <module name="IllegalInstantiation"/>
 

Example:

 public class MyTest {
   public class Boolean {
     boolean a;

     public Boolean (boolean a) { this.a = a; }
   }

   public void myTest (boolean a, int b) {
     Boolean c = new Boolean(a); // OK
     java.lang.Boolean d = new java.lang.Boolean(a); // OK

     Integer e = new Integer(b); // OK
     Integer f = Integer.valueOf(b); // OK
   }
 }
 

To configure the check to find instantiations of java.lang.Boolean and java.lang.Integer. NOTE: Even if property tokens is completely removed from the following configuration, Checkstyle will produce the same results for violation. This is because if property tokens is not defined in the configuration, Checkstyle will supply it with list of default tokens CLASS_DEF, LITERAL_NEW, PACKAGE_DEF, IMPORT for this check. The property is defined in this example only to provide clarity:

 <module name="IllegalInstantiation">
   <property name="classes" value="java.lang.Boolean,
     java.lang.Integer"/>
   <property name="tokens" value="CLASS_DEF, LITERAL_NEW,
     PACKAGE_DEF, IMPORT"/>
 </module>
 

Example:

 public class MyTest {
   public class Boolean {
     boolean a;

     public Boolean (boolean a) { this.a = a; }
   }

   public void myTest (boolean a, int b) {
     Boolean c = new Boolean(a); // OK
     java.lang.Boolean d = new java.lang.Boolean(a); // violation, instantiation of
                                                     // java.lang.Boolean should be avoided

     Integer e = new Integer(b); // violation, instantiation of
                                 // java.lang.Integer should be avoided
     Integer f = Integer.valueOf(b); // OK
   }
 }
 

To configure the check to allow violations for local classes vs classes defined in the check, for example java.lang.Boolean, property tokens must be defined to not mention CLASS_DEF, so its value should be LITERAL_NEW, PACKAGE_DEF, IMPORT:

 <module name="IllegalInstantiation">
   <property name="classes" value="java.lang.Boolean,
     java.lang.Integer"/>
   <property name="tokens" value="LITERAL_NEW, PACKAGE_DEF,
     IMPORT"/>
 </module>
 

Example:

 public class MyTest {
   public class Boolean {
     boolean a;

     public Boolean (boolean a) { this.a = a; }
   }

   public void myTest (boolean a, int b) {
     Boolean c = new Boolean(a); // violation, instantiation of
                                 // java.lang.Boolean should be avoided
     java.lang.Boolean d = new java.lang.Boolean(a); // violation, instantiation of
                                                     // java.lang.Boolean should be avoided

     Integer e = new Integer(b); // violation, instantiation of
                                 // java.lang.Integer should be avoided
     Integer f = Integer.valueOf(b); // OK
   }
 }
 

Finally, there is a limitation that it is currently not possible to specify array classes:

 <module name="IllegalInstantiation">
   <property name="classes" value="java.lang.Boolean[],
      Boolean[], java.lang.Integer[], Integer[]"/>
 </module>
 

Example:

 public class MyTest {
   public void myTest () {
     Boolean[] newBoolArray = new Boolean[]{true,true,false}; // OK
     Integer[] newIntArray = new Integer[]{1,2,3}; // OK
   }
 }
 

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

• instantiation.avoid

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
private java.util.Set<java.lang.String>	classes Specify fully qualified class names that should not be instantiated.
private java.util.Set<java.lang.String>	classNames The class names defined in the file.
private java.util.Set<FullIdent>	imports The imports for the file.
private java.util.Set<DetailAST>	instantiations The instantiations in the file.
private static java.lang.String	JAVA_LANG java.lang package as string.
static java.lang.String	MSG_KEY A key is pointing to the warning message text in "messages.properties" file.
private java.lang.String	pkgName Name of the package.

Constructor Summary

Constructors

Constructor and Description
IllegalInstantiationCheck()

Method Summary

Modifier and Type	Method and Description
void	beginTree(DetailAST rootAST) Called before the starting to process a tree.
private java.lang.String	checkImportStatements(java.lang.String className) Check import statements.
void	finishTree(DetailAST rootAST) Called after finished processing a tree.
int[]	getAcceptableTokens() The configurable token set.
int[]	getDefaultTokens() Returns the default token a check is interested in.
private java.lang.String	getIllegalInstantiation(java.lang.String className) Checks illegal instantiations.
int[]	getRequiredTokens() The tokens that this check must be registered for.
private boolean	isSamePackage(java.lang.String className, int pkgNameLen, java.lang.String illegal) Check that type is of the same package.
private boolean	isStandardClass(java.lang.String className, java.lang.String illegal) Is Standard Class.
private void	postProcessLiteralNew(DetailAST newTokenAst) Processes one of the collected "new" tokens when walking tree has finished.
private void	processClassDef(DetailAST ast) Collects classes defined in the source file.
private void	processImport(DetailAST ast) Perform processing for an import token.
private void	processLiteralNew(DetailAST ast) Collects a "new" token.
private void	processPackageDef(DetailAST ast) Perform processing for an package token.
void	setClasses(java.lang.String... names) Setter to specify fully qualified class names that should not be instantiated.
void	visitToken(DetailAST ast) Called to process a token.

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

clearViolations, destroy, 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

public static final java.lang.String MSG_KEY

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

See Also:

Constant Field Values

JAVA_LANG

private static final java.lang.String JAVA_LANG

java.lang package as string.

See Also:

Constant Field Values

imports

private final java.util.Set<FullIdent> imports

The imports for the file.

classNames

private final java.util.Set<java.lang.String> classNames

The class names defined in the file.

instantiations

private final java.util.Set<DetailAST> instantiations

The instantiations in the file.

classes

private java.util.Set<java.lang.String> classes

Specify fully qualified class names that should not be instantiated.

pkgName

private java.lang.String pkgName

Name of the package.

Constructor Detail

IllegalInstantiationCheck

public IllegalInstantiationCheck()

Method Detail

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

beginTree

public void beginTree(DetailAST rootAST)

Description copied from class: AbstractCheck

Called before the starting to process a tree. Ideal place to initialize information that is to be collected whilst processing a tree.

Overrides:

beginTree in class AbstractCheck

Parameters:

rootAST - the root of the tree

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

finishTree

public void finishTree(DetailAST rootAST)

Description copied from class: AbstractCheck

Called after finished processing a tree. Ideal place to report on information collected whilst processing a tree.

Overrides:

finishTree in class AbstractCheck

Parameters:

rootAST - the root of the tree

processClassDef

private void processClassDef(DetailAST ast)

Collects classes defined in the source file. Required to avoid false alarms for local vs. java.lang classes.

Parameters:

ast - the class def token.

processImport

private void processImport(DetailAST ast)

Perform processing for an import token.

Parameters:

ast - the import token

processPackageDef

private void processPackageDef(DetailAST ast)

Perform processing for an package token.

Parameters:

ast - the package token

processLiteralNew

private void processLiteralNew(DetailAST ast)

Collects a "new" token.

Parameters:

ast - the "new" token

postProcessLiteralNew

private void postProcessLiteralNew(DetailAST newTokenAst)

Processes one of the collected "new" tokens when walking tree has finished.

Parameters:

newTokenAst - the "new" token.

getIllegalInstantiation

private java.lang.String getIllegalInstantiation(java.lang.String className)

Checks illegal instantiations.

Parameters:

className - instantiated class, may or may not be qualified

Returns:

the fully qualified class name of className or null if instantiation of className is OK

checkImportStatements

private java.lang.String checkImportStatements(java.lang.String className)

Check import statements.

Parameters:

className - name of the class

Returns:

value of illegal instantiated type

isSamePackage

private boolean isSamePackage(java.lang.String className,
                              int pkgNameLen,
                              java.lang.String illegal)

Check that type is of the same package.

Parameters:

className - class name

pkgNameLen - package name

illegal - illegal value

Returns:

true if type of the same package

isStandardClass

private boolean isStandardClass(java.lang.String className,
                                java.lang.String illegal)

Is Standard Class.

Parameters:

className - class name

illegal - illegal value

Returns:

true if type is standard

setClasses

public void setClasses(java.lang.String... names)

Setter to specify fully qualified class names that should not be instantiated.

Parameters:

names - a comma separate list of class names