AvoidNestedBlocks

Since Checkstyle 3.1

Description

Finds nested blocks (blocks that are used freely in the code).

Rationale: Nested blocks are often leftovers from the debugging process, they confuse the reader.

For example, this check finds the obsolete braces in 

public void guessTheOutput()
{
  int whichIsWhich = 0;
  {
    whichIsWhich = 2;
  }
  System.out.println("value = " + whichIsWhich);
}

and debugging / refactoring leftovers such as 

// if (conditionThatIsNotUsedAnyLonger)
{
  System.out.println("unconditional");
}

A case in a switch statement does not implicitly form a block. Thus, to be able to introduce local variables that have case scope it is necessary to open a nested block. This is supported, set the allowInSwitchCase property to true and include all statements of the case in the block.

Properties

name description type default value since
allowInSwitchCase Allow nested blocks if they are the only child of a switch case. boolean false 3.2

Examples

To configure the check:

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

Example:

public class Example1 {
  public void foo() {
    int myInteger = 0;
    {                      // violation
      myInteger = 2;
    }
    System.out.println("myInteger = " + myInteger);

    switch (a) {
      case 1: {                    // violation
        System.out.println("Case 1");
        break;
      }
      case 2:
        System.out.println("Case 2");
        break;
    }
  }
}

To configure the check to allow nested blocks in switch case:

<module name="Checker">
  <module name="TreeWalker">
    <module name="AvoidNestedBlocks">
      <property name="allowInSwitchCase" value="true"/>
    </module>
  </module>
</module>

Example:

public class Example2 {
  public void foo() {
    int myInteger = 0;
    {                      // violation
      myInteger = 2;
    }
    System.out.println("myInteger = " + myInteger);

    switch (a) {
      case 1: {
        System.out.println("Case 1");
        break;
      }
      case 2:
        System.out.println("Case 2");
        break;
    }
  }
}

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.blocks

Parent Module

TreeWalker