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;
}
}
| name | description | type | default value |
|---|---|---|---|
| allowInSwitchCase | Allow nested blocks in case statements | boolean | false |
All messages can be customized if the default message doesn't suite you. Please see the documentation to learn how to.
| name | description | type | default value |
|---|---|---|---|
| option | policy on block contents | block policy | stmt |
| tokens | tokens to check | subset of tokens LITERAL_WHILE, LITERAL_TRY, LITERAL_CATCH, LITERAL_FINALLY, LITERAL_DO, LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, INSTANCE_INIT, STATIC_INIT, LITERAL_SWITCH, LITERAL_SYNCHRONIZED, LITERAL_CASE, LITERAL_DEFAULT, ARRAY_INIT. | LITERAL_WHILE, LITERAL_TRY, LITERAL_FINALLY, LITERAL_DO, LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, INSTANCE_INIT, STATIC_INIT, LITERAL_SWITCH, LITERAL_SYNCHRONIZED. |
To configure the check:
<module name="EmptyBlock"/>
To configure the check for the text policy and only try blocks:
<module name="EmptyBlock">
<property name="option" value="text"/>
<property name="tokens" value="LITERAL_TRY"/>
</module>
All messages can be customized if the default message doesn't suite you. Please see the documentation to learn how to.
Checks for empty catch blocks. There are two options to make validation more precise (by default Check allows empty catch block with any comment inside):
| name | description | type | default value |
|---|---|---|---|
| exceptionVariableName | The name of variable associated with exception | String | ^$ |
| commentFormat | The format of the first comment inside empty catch | String | .* |
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>
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>
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) {
}
All messages can be customized if the default message doesn't suite you. Please see the documentation to learn how to.
Checks for the placement of left curly braces ('{') for code blocks. The policy to verify is specified using the property option. Policies eol and nlow take into account the property maxLineLength.
| name | description | type | default value |
|---|---|---|---|
| option | policy on placement of a left curly brace ('{') | left curly brace policy | eol |
| ignoreEnums | If true, Check will ignore enums when left curly brace policy is EOL | boolean | true |
| maxLineLength | maximum number of characters in a line. ATTENTION: The option has been marked as deprecated since checkstyle 6.10 release. | integer | 80 |
| tokens | tokens to check | subset of tokens INTERFACE_DEF, CLASS_DEF, ANNOTATION_DEF, ENUM_DEF, CTOR_DEF, METHOD_DEF, ENUM_CONSTANT_DEF, LITERAL_WHILE, LITERAL_TRY, LITERAL_CATCH, LITERAL_FINALLY, LITERAL_SYNCHRONIZED, LITERAL_SWITCH, LITERAL_DO, LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, STATIC_INIT, OBJBLOCK, LAMBDA. | INTERFACE_DEF, CLASS_DEF, ANNOTATION_DEF, ENUM_DEF, CTOR_DEF, METHOD_DEF, ENUM_CONSTANT_DEF, LITERAL_WHILE, LITERAL_TRY, LITERAL_CATCH, LITERAL_FINALLY, LITERAL_SYNCHRONIZED, LITERAL_SWITCH, LITERAL_DO, LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, STATIC_INIT, OBJBLOCK, LAMBDA. |
To configure the check:
<module name="LeftCurly"/>
To configure the check to apply the nl policy to type blocks:
<module name="LeftCurly">
<property name="option" value="nl"/>
<property name="tokens" value="CLASS_DEF,INTERFACE_DEF"/>
</module>
An example of how to configure the check to validate enum definitions:
<module name="LeftCurly">
<property name="ignoreEnums" value="false"/>
</module>
All messages can be customized if the default message doesn't suite you. Please see the documentation to learn how to.
| name | description | type | default value |
|---|---|---|---|
| allowSingleLineStatement | allows single-line statements without braces | boolean | false |
| allowEmptyLoopBody | allows loops with empty bodies | boolean | false |
| tokens | tokens to check | subset of tokens LITERAL_DO, LITERAL_ELSE, LITERAL_FOR, LITERAL_IF, LITERAL_WHILE, LITERAL_CASE, LITERAL_DEFAULT, LAMBDA. | LITERAL_DO, LITERAL_ELSE, LITERAL_FOR, LITERAL_IF, LITERAL_WHILE. |
To configure the check:
<module name="NeedBraces"/>
To configure the check for if and else blocks:
<module name="NeedBraces">
<property name="tokens" value="LITERAL_IF, LITERAL_ELSE"/>
</module>
To configure the check to allow single-line statements (if, while, do-while, for) without braces:
<module name="NeedBraces">
<property name="allowSingleLineStatement" value="true"/>
</module>
Next statements won't be violated by Check:
if (obj.isValid()) return true; // OK
while (obj.isValid()) return true; // OK
do this.notify(); while (o != null); // OK
for (int i = 0; ; ) this.notify(); // OK
To configure the Check to allow case, default single-line statements without braces:
<module name="NeedBraces">
<property name="tokens" value="LITERAL_CASE, LITERAL_DEFAULT"/>
<property name="allowSingleLineStatement" value="true"/>
</module>
Next statements won't be violated by Check:
switch (num) {
case 1: counter++; break; // OK
case 6: counter += 10; break; // OK
default: counter = 100; break; // OK
}
To configure the check to allow loops (while, for) with empty bodies:
<module name="NeedBraces">
<property name="allowEmptyLoopBody" value="true"/>
</module>
Next statements won't be violated by Check:
while (value.incrementValue() < 5); // OK
for(int i = 0; i < 10; value.incrementValue()); // OK
All messages can be customized if the default message doesn't suite you. Please see the documentation to learn how to.
Checks the placement of right curly braces ('}') for if-else, try-catch-finally blocks, while-loops, for-loops, method definitions, class definitions, constructor definitions, instance and static initialization blocks. The policy to verify is specified using the property option.
| name | description | type | default value |
|---|---|---|---|
| option | policy on placement of a right curly brace ('}') | right curly brace policy | same |
| shouldStartLine | should we check if '}' starts line. | boolean | true |
| tokens | tokens to check | subset of tokens LITERAL_TRY, LITERAL_CATCH, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE, CLASS_DEF, METHOD_DEF, CTOR_DEF, LITERAL_FOR, LITERAL_WHILE, LITERAL_DO, STATIC_INIT, INSTANCE_INIT. | LITERAL_TRY, LITERAL_CATCH, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE. |
To configure the check:
<module name="RightCurly"/>
To configure the check with policy alone for else and METHOD_DEF tokens:
<module name="RightCurly">
<property name="option" value="alone"/>
<property name="tokens" value="LITERAL_ELSE, METHOD_DEF"/>
</module>
All messages can be customized if the default message doesn't suite you. Please see the documentation to learn how to.