FallThrough

Since Checkstyle 3.4

Description

Checks for fall-through in switch statements. Finds locations where a case contains Java code but lacks a break, return, yield, throw or continue statement.

The check honors special comments to suppress the warning. By default, the texts "fallthru", "fall thru", "fall-thru", "fallthrough", "fall through", "fall-through" "fallsthrough", "falls through", "falls-through" (case-sensitive). The comment containing these words must be all on one line, and must be on the last non-empty line before the case triggering the warning or on the same line before the case (ugly, but possible). Any other comment may follow on the same line.

Note: The check assumes that there is no unreachable code in the case.

Properties

name	description	type	default value	since
checkLastCaseGroup	Control whether the last case group must be checked.	boolean	`false`	4.0
reliefPattern	Define the RegExp to match the relief comment that suppresses the warning about a fall through.	Pattern	`"falls?[ -]?thr(u\|ough)"`	4.0

Examples

To configure the check:


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

Example:


class Example1 {
  public void foo() throws Exception {
    int i = 0;
    while (i >= 0) {
      switch (i) {
        case 1:
          i++;
          /* block */ /* fallthru */ // comment
        case 2: // ok, ReliefPattern is present in above line.
          i++;
          break;
        case 3:
          i++;
          return;
        case 4:
          i++;
          throw new Exception();
        case 5:
          i++; // no break by design
        case 6: // violation 'Fall\ through from previous branch of the switch'
        case 7:
          i++;
          continue;
        case 11:
          i++;
      }
    }
  }
}

To configure the check to enable check for last case group:


<module name="Checker">
  <module name="TreeWalker">
    <module name="FallThrough">
      <property name="checkLastCaseGroup" value="true"/>
    </module>
  </module>
</module>

Example:


class Example2 {
  public void foo() throws Exception {
    int i = 0;
    while (i >= 0) {
      switch (i) {
        case 1:
          i++;
        case 2: // violation 'Fall\ through from previous branch of the switch'
          i++;
          break;
        case 3:
          i++;
          return;
        case 4:
          i++;
          throw new Exception();
        case 5:
          i++; // no break by design
        case 6: // violation 'Fall\ through from previous branch of the switch'
        case 7:
          i++;
          continue;
        case 11: // violation 'Fall\ through from the last branch of the switch'
          i++;
      }
    }
  }
}

To configure the check with custom relief pattern:


<module name="Checker">
  <module name="TreeWalker">
    <module name="FallThrough">
      <property name="reliefPattern" value="no break by design"/>
    </module>
  </module>
</module>

Example:


class Example3 {
  public void foo() throws Exception {
    int i = 0;
    while (i >= 0) {
      switch (i) {
        case 1:
          i++;
        case 2: // violation 'Fall\ through from previous branch of the switch'
          i++;
          break;
        case 3:
          i++;
          return;
        case 4:
          i++;
          throw new Exception();
        case 5:
          i++; // no break by design
        case 6:
        case 7:
          i++;
          continue;
        case 11:
          i++;
      }
    }
  }
}

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