HiddenField

Since Checkstyle 3.0

Description

Checks that a local variable or a parameter does not shadow a field that is defined in the same class.

Notes

It is possible to configure the check to ignore all property setter methods.

A method is recognized as a setter if it is in the following form 

${returnType} set${Name}(${anyType} ${name}) { ... }

where ${anyType} is any primitive type, class or interface name; ${name} is name of the variable that is being set and ${Name} its capitalized form that appears in the method name. By default, it is expected that setter returns void, i.e. ${returnType} is 'void'. For example 

void setTime(long time) { ... }

Any other return types will not let method match a setter pattern. However, by setting setterCanReturnItsClass property to true definition of a setter is expanded, so that setter return type can also be a class in which setter is declared. For example 

class PageBuilder {
  PageBuilder setName(String name) { ... }
}

Such methods are known as chain-setters and a common when Builder-pattern is used. Property setterCanReturnItsClass has effect only if ignoreSetter is set to true.

Properties

name description type default value since
ignoreAbstractMethods Control whether to ignore parameters of abstract methods. boolean false 4.0
ignoreConstructorParameter Control whether to ignore constructor parameters. boolean false 3.2
ignoreFormat Define the RegExp for names of variables and parameters to ignore. Pattern null 3.2
ignoreSetter Allow to ignore the parameter of a property setter method. boolean false 3.2
setterCanReturnItsClass Allow to expand the definition of a setter method to include methods that return the class' instance. boolean false 6.3
tokens tokens to check subset of tokens VARIABLE_DEF , PARAMETER_DEF , PATTERN_VARIABLE_DEF , LAMBDA , RECORD_COMPONENT_DEF . VARIABLE_DEF , PARAMETER_DEF , PATTERN_VARIABLE_DEF , LAMBDA , RECORD_COMPONENT_DEF . 3.0

Examples

To configure the check: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="HiddenField"/>
  </module>
</module>

Example:

class Example1 {

  private String field;
  private String testField;

  Example1(String testField) { // violation, 'field' hides a field
  }
  void method(String param) {
    String field = param; // violation, ''field' hides a field'
  }
  void setTestField(String testField) { // violation, ''testField' hides a field'
    this.field = field;
  }
  Example1 setField(String field) { // violation, ''field' hides a field'
    this.field = field;
    return null;
  }
  abstract class Inner {
    abstract int method(String field); // violation, ''field' hides a field'
  }
}

To configure the check so that it checks local variables but not parameters: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="HiddenField">
      <property name="tokens" value="VARIABLE_DEF"/>
    </module>
  </module>
</module>

Example:

class Example2 {

  private String field;
  private String testField;

  Example2(String testField) { // OK, because PARAMETER_DEF not configured
  }
  void method(String param) {
    String field = param; // violation, ''field' hides a field'
  }
  void setTestField(String testField) { // OK, because PARAMETER_DEF not configured
    this.field = field;
  }
  Example2 setField(String field) { // OK, because PARAMETER_DEF not configured
    this.field = field;
    return null;
  }
  abstract class Inner {
    abstract int method(String field); // OK, because PARAMETER_DEF not configured
  }
}

To configure the check so that it ignores the variables and parameters named "test": 

<module name="Checker">
  <module name="TreeWalker">
    <module name="HiddenField">
      <property name="ignoreFormat" value="^testField"/>
    </module>
  </module>
</module>

Example:

class Example3 {

  private String field;
  private String testField;

  Example3(String testField) { // OK, because it match ignoreFormat
  }
  void method(String param) {
    String field = param; // violation, ''field' hides a field'
  }
  void setTestField(String testField) { // OK, because it match ignoreFormat
    this.field = field;
  }
  Example3 setField(String field) { // violation, ''field' hides a field'
    this.field = field;
    return null;
  }
  abstract class Inner {
    abstract int method(String field); // violation, ''field' hides a field'
  }
}

To configure the check so that it ignores constructor parameters: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="HiddenField">
      <property name="ignoreConstructorParameter" value="true"/>
    </module>
  </module>
</module>

Example:

class Example4 {

  private String field;
  private String testField;

  Example4(String testField) { // OK, because ignoreConstructorParameter is true
  }
  void method(String param) {
    String field = param; // violation, ''field' hides a field' field
  }
  void setTestField(String testField) { // violation, ''testField' hides a field'
    this.field = field;
  }
  Example4 setField(String field) { // violation, ''field' hides a field'
    this.field = field;
    return null;
  }
  abstract class Inner {
    abstract int method(String field); // violation, ''field' hides a field'
  }
}

To configure the check so that it ignores the parameter of setter methods: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="HiddenField">
      <property name="ignoreSetter" value="true"/>
    </module>
  </module>
</module>

Example:

class Example5 {

  private String field;
  private String testField;

  Example5(String testField) { // violation, ''testField' hides a field'
  }
  void method(String param) {
    String field = param; // violation, ''field' hides a field'
  }
  void setTestField(String testField) { // OK, because ignoreSetter is true
    this.field = field;
  }
  Example5 setField(String field) { // violation, ''field' hides a field'
    this.field = field;
    return null;
  }
  abstract class Inner {
    abstract int method(String field); // violation, ''field' hides a field'
  }
}

To configure the check so that it ignores the parameter of setter methods recognizing setter as returning either void or a class in which it is declared: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="HiddenField">
      <property name="ignoreSetter" value="true"/>
      <property name="setterCanReturnItsClass" value="true"/>
    </module>
  </module>
</module>

Example:

class Example6 {

  private String field;
  private String testField;

  Example6(String testField) { // violation, ''testField' hides a field'
  }
  void method(String param) {
    String field = param; // violation, ''field' hides a field'
  }
  void setTestField(String testField) { // OK, because ignoreSetter is true
    this.field = field;
  }
  Example6 setField(String field) { // OK, because setterCanReturnItsClass is true
    this.field = field;
    return null;
  }
  abstract class Inner {
    abstract int method(String field); // violation, ''field' hides a field'
  }
}

To configure the check so that it ignores parameters of abstract methods: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="HiddenField">
      <property name="ignoreAbstractMethods" value="true"/>
    </module>
  </module>
</module>

Example:

class Example7 {

  private String field;
  private String testField;

  Example7(int field) { // violation, ''field' hides a field'
    this.field = Integer.toString(field);
  }
  void method(String param) {
    String field = param; // violation, ''field' hides a field'
  }
  void setTestField(String testField) { // violation, 'testField' hides a field'
    this.field = field;
  }
  Example7 setField(String field) { // violation, ''field' hides a field'
    this.field = field;
    return null;
  }
  abstract class Inner {
    abstract int method(String field); // OK, because ignoreAbstractMethods is true
  }
}

Example of Usage

Violation Messages

All messages can be customized if the default message doesn't suit you. Please see the documentation to learn how to.

Package

com.puppycrawl.tools.checkstyle.checks.coding

Parent Module

TreeWalker