AvoidNestedBlocks.md

Pattern: Use of nested block

Issue: -

Description

Finds nested blocks, i.e. 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;
    {
        int 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.

switch (a)
{
    case 0:
        // Never OK, break outside block
        {
   x = 1;
        }
        break;
    case 1:
        // Never OK, statement outside block
        System.out.println("Hello");
        {
   x = 2;
   break;
        }
    case 1:
        // OK if allowInSwitchCase is true
        {
   System.out.println("Hello");
   x = 2;
   break;
        }
}

Examples

To configure the check:

<module name="AvoidNestedBlocks"/>

Further Reading

• checkstyle - AvoidNestedBlocks