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:

public class SomeClass {

  private String field;
  private String testField;

  public SomeClass(String testField) { // violation, 'testField' param hides 'testField' field
  }
  public void method(String param) { // OK
      String field = param; // violation, 'field' variable hides 'field' field
  }
  public void setTestField(String testField) { // violation, 'testField' param
                                               // hides 'testField' field
      this.field = field;
  }
  public SomeClass setField(String field) { // violation, 'field' param hides 'field' field
      this.field = 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:

public class SomeClass {

  private String field;
  private String testField;

  public SomeClass(String testField) { // OK, 'testField' param doesn't hide any field
  }
  public void method(String param) { // OK
      String field = param; // violation, 'field' variable hides 'field' field
  }
  public void setTestField(String testField) { // OK, 'testField' param doesn't hide any field
      this.field = field;
  }
  public SomeClass setField(String field) { // OK, 'field' param doesn't hide any field
      this.field = field;
  }
}

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:

public class SomeClass {

  private String field;
  private String testField;

  public SomeClass(String testField) { // OK, because it match ignoreFormat
  }
  public void method(String param) { // OK
      String field = param; // violation, 'field' variable hides 'field' field
  }
  public void setTestField(String testField) { // OK, because it match ignoreFormat
      this.field = field;
  }
  public SomeClass setField(String field) { // violation, 'field' param hides 'field' field
      this.field = 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:

public class SomeClass {

  private String field;
  private String testField;

  public SomeClass(String testField) { // OK, 'testField' param doesn't hide any field
  }
  public void method(String param) { // OK
      String field = param; // violation, 'field' variable hides 'field' field
  }
  public void setTestField(String testField) { // violation, 'testField' variable
                                               // hides 'testField' field
      this.field = field;
  }
  public SomeClass setField(String field) { // violation, 'field' param hides 'field' field
      this.field = 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:

public class SomeClass {

  private String field;
  private String testField;

  public SomeClass(String testField) { // violation, 'testField' param hides 'testField' field
  }
  public void method(String param) { // OK
      String field = param; // violation, 'field' variable hides 'field' field
  }
  public void setTestField(String testField) { // OK, 'testField' param doesn't hide any field
      this.field = field;
  }
  public SomeClass setField(String field) { // violation, 'field' param hides 'field' field
      this.field = 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:

public class SomeClass {

  private String field;
  private String testField;

  public SomeClass(String testField) { // violation, 'testField' param hides 'testField' field
  }
  public void method(String param) { // OK
      String field = param; // violation, 'field' variable hides 'field' field
  }
  public void setTestField(String testField) { // OK, 'testField' param doesn't hide any field
      this.field = field;
  }
  public SomeClass setField(String field) { // OK, 'field' param doesn't hide any field
      this.field = 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:

abstract class SomeClass {

  private String field;

  public SomeClass(int field) { // violation, 'field' param hides a 'field' field
    float field; // violation, 'field' variable hides a 'field' field
  }
  public abstract int method(String field); // OK
}

public class Demo extends SomeClass {

  public int method(String param){
    return param;
  }
}

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