Description

Warning: the Check is very controversial if 'validateOnlyOverlapping' option is set to 'false' and not that actual nowadays.

Rationale:

1. The same notation/habit for C++ and Java (C++ have global methods, so having "this." do make sense in it to distinguish call of method of class instead of global).
2. Non-IDE development (ease of refactoring, some clearness to distinguish static and non-static methods).

Notes

Limitations: Nothing is currently done about static variables or catch-blocks. Static methods invoked on a class name seem to be OK; both the class name and the method name have a DOT parent. Non-static methods invoked on either this or a variable name seem to be OK, likewise.

Properties

Examples

To configure the default check:

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

Example:

class Example1 {
  int field1,field2,field3;

  Example1(int field1) {
    this.field1 = field1;
    field2 = 0;
    foo(5); // OK, methods cannot be overlapped in java.
  }

  void method2(int i) {
    foo(i); // OK, methods cannot be overlapped in java.
  }

  void foo(int field3) {
    // violation below, reference to instance variable "field3" requires "this"
    field3 = field3;
  }
}
        

Note that method call foo(5) does not raise a violation because methods cannot be overlapped in java.

To configure the check demand methods and fields to have 'this.'

<module name="Checker">
  <module name="TreeWalker">
    <module name="RequireThis">
      <property name="validateOnlyOverlapping" value="false"/>
    </module>
  </module>
</module>
        

Example:

class Example4 {
  int field1,field2,field3;

  Example4(int field1) {
    this.field1 = field1;
    field2 = 0; // violation, reference to instance variable "field2" requires "this"
    foo(5); // violation, method call "foo(5)" requires "this"
  }

  void method2(int i) {
    foo(i); // violation, 'Method call to 'foo' needs "this.".'
  }

  void foo(int field3) {
    // violation below, reference to instance variable "field3" requires "this"
    field3 = field3;
  }
}
        

To configure the check demand fields only to have 'this.'

<module name="Checker">
  <module name="TreeWalker">
    <module name="RequireThis">
      <property name="validateOnlyOverlapping" value="false"/>
      <property name="checkMethods" value="false"/>
    </module>
  </module>
</module>
        

Example:

class Example2 {
  int field1,field2,field3;

  Example2(int field1) {
    this.field1 = field1;
    field2 = 0; // violation, reference to instance variable "field2" requires "this"
    foo(5); // OK, checkMethods is false
  }

  void method2(int i) {
    foo(i); // OK, checkMethods is false
  }

  void foo(int field3) {
    // violation below, reference to instance variable "field3" requires "this"
    field3 = field3;
  }
}
        

To configure the check demand methods only to have 'this.'

<module name="Checker">
  <module name="TreeWalker">
    <module name="RequireThis">
      <property name="validateOnlyOverlapping" value="false"/>
      <property name="checkFields" value="false"/>
    </module>
  </module>
</module>
        

Example:

class Example3 {
  int field1,field2,field3;

  Example3(int field1) {
    this.field1 = field1;
    field2 = 0;
    foo(5); // violation, method call "foo(5)" requires "this"
  }

  void method2(int i) {
    foo(i); // violation, 'Method call to 'foo' needs "this.".'
  }

  void foo(int field3) {

    field3 = field3;
  }
}
        

Please, be aware of the following logic, which is implemented in the check:

1) If you arrange 'this' in your code on your own, the check will not raise violation for variables which use 'this' to reference a class field, for example:

class Example5 {
  int field1,field2;

  public void foo(int field1) {
    field1 = this.field1;

    if (field1 > 0) {
      field1 = -field1;
    }
    // violation below, reference to instance variable "field2" requires "this"
    field2 *= field1;
  }
}
        

2) If method parameter is returned from the method, the check will not raise violation for returned variable/parameter, for example:

class Example6 {
  String prefix;

  String modifyPrefix(String prefix) {
    prefix = "^" + prefix + "$";  //OK, because method parameter is returned
    return prefix;
  }
}
        

Example of Usage

• Checkstyle Style

Violation Messages

• require.this.method
• require.this.variable

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