EmptyCatchBlock

Since Checkstyle 6.4

Description

Checks for empty catch blocks. By default, check allows empty catch block with any comment inside.

Notes

There are two options to make validation more precise: exceptionVariableName and commentFormat. If both options are specified - they are applied by any of them is matching.

Properties

name description type default value since
exceptionVariableName Specify the RegExp for the name of the variable associated with exception. If check meets variable name matching specified value - empty block is suppressed. Pattern "^$" 6.4
commentFormat Specify the RegExp for the first comment inside empty catch block. If check meets comment inside empty catch block matching specified format - empty block is suppressed. If it is multi-line comment - only its first line is analyzed. Pattern ".*" 6.4

Examples

To configure the check: 

<module name="EmptyCatchBlock"/>

Example: 

try {
  throw new RuntimeException();
} catch (RuntimeException expected) {
} // violation

try {
  throw new RuntimeException();
} catch (RuntimeException ignore) {
  // no handling
} // ok, catch block has comment

try {
  throw new RuntimeException();
} catch (RuntimeException o) {
} // violation

try {
  throw new RuntimeException();
} catch (RuntimeException ex) {
  // This is expected
} // ok

To configure the check to suppress empty catch block if exception's variable name is expected or ignore or there's any comment inside: 

<module name="EmptyCatchBlock">
  <property name="exceptionVariableName" value="expected|ignore"/>
</module>

Such empty blocks would be both suppressed: 

try {
  throw new RuntimeException();
} catch (RuntimeException expected) {
} // ok

try {
  throw new RuntimeException();
} catch (RuntimeException ignore) {
  // no handling
} // ok

try {
  throw new RuntimeException();
} catch (RuntimeException o) {
} // violation

try {
  throw new RuntimeException();
} catch (RuntimeException ex) {
  // This is expected
} // ok

To configure the check to suppress empty catch block if single-line comment inside is "//This is expected": 

<module name="EmptyCatchBlock">
  <property name="commentFormat" value="This is expected"/>
</module>

Such empty block would be suppressed: 

try {
  throw new RuntimeException();
} catch (RuntimeException expected) {
} // violation

try {
  throw new RuntimeException();
} catch (RuntimeException ignore) {
  // no handling
} // violation

try {
  throw new RuntimeException();
} catch (RuntimeException o) {
} // violation

try {
  throw new RuntimeException();
} catch (RuntimeException ex) {
  // This is expected
} // ok

To configure the check to suppress empty catch block if single-line comment inside is "//This is expected" or exception's variable name is "myException" (any option is matching): 

<module name="EmptyCatchBlock">
  <property name="commentFormat" value="This is expected"/>
  <property name="exceptionVariableName" value="myException"/>
</module>

Such empty blocks would be suppressed: 

try {
  throw new RuntimeException();
} catch (RuntimeException e) {
  //This is expected
}
...
try {
  throw new RuntimeException();
} catch (RuntimeException e) {
  //   This is expected
}
...
try {
  throw new RuntimeException();
} catch (RuntimeException e) {
  // This is expected
  // some another comment
}
...
try {
  throw new RuntimeException();
} catch (RuntimeException e) {
  /* This is expected */
}
...
try {
  throw new RuntimeException();
} catch (RuntimeException e) {
  /*
  *
  * This is expected
  * some another comment
  */
}
...
try {
  throw new RuntimeException();
} catch (RuntimeException myException) {

}

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