Since Checkstyle 3.0
Checks for braces around code blocks.
| name | description | type | default value | since |
|---|---|---|---|---|
| allowEmptyLoopBody | Allow loops with empty bodies. | boolean | false |
6.12.1 |
| allowSingleLineStatement | Allow single-line statements without braces. | boolean | false |
6.5 |
| 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 . | 3.0 |
To configure the check:
<module name="Checker">
<module name="TreeWalker">
<module name="NeedBraces"/>
</module>
</module>
Example:
class Example1 {
String obj = new String();
String value = new String();
int counter = 1;
int count = 0;
int num = 12;
String o = "O";
public boolean Example1() {
if (obj.equals(num)) return true;
// violation above, ''if' construct must use '{}'s.'
if (true) {
count = 2;
} else
// violation above, ''else' construct must use '{}'s.'
return false;
for (int i = 0; i < 5; i++) {
++count;}
do // violation, ''do' construct must use '{}'s.'
++count;
while (false);
for (int j = 0; j < 10; j++);
// violation above, ''for' construct must use '{}'s.'
for(int i = 0; i < 10; value.charAt(12));
// violation above, ''for' construct must use '{}'s.'
while (counter < 10)
// violation above, ''while' construct must use '{}'s.'
++count;
while (value.charAt(12) < 5);
// violation above, ''while' construct must use '{}'s.'
switch (num) {
case 1: counter++; break;
}
return true;
}
}
To configure the check for if and
else blocks:
<module name="Checker">
<module name="TreeWalker">
<module name="NeedBraces">
<property name="tokens" value="LITERAL_IF, LITERAL_ELSE"/>
</module>
</module>
</module>
Example:
class Example2 {
String obj = new String();
String value = new String();
int counter = 1;
int count = 0;
int num = 12;
String o = "O";
public boolean Example2() {
if (obj.equals(num)) return true;
// violation above, ''if' construct must use '{}'s.'
if (true) {
count = 2;
} else
// violation above, ''else' construct must use '{}'s.'
return false;
for (int i = 0; i < 5; i++) {
++count;}
do // ok, because DO is not a target of validation
++count;
while (false);
for (int j = 0; j < 10; j++);
// ok above, because FOR is not a target of validation
for(int i = 0; i < 10; value.charAt(12));
// ok above, because FOR is not a target of validation
while (counter < 10)
// ok above, because WHILE is not a target of validation
++count;
while (value.charAt(12) < 5);
// ok above, because WHILE is not a target of validation
switch (num) {
case 1: counter++; break;
}
return true;
}
}
To configure the check to allow single-line statements
(if, while, do-while, for) without braces:
<module name="Checker">
<module name="TreeWalker">
<module name="NeedBraces">
<property name="allowSingleLineStatement" value="true"/>
<property name="tokens"
value="LITERAL_IF, LITERAL_WHILE, LITERAL_DO, LITERAL_FOR"/>
</module>
</module>
</module>
Example:
class Example3 {
String obj = new String();
String value = new String();
int counter = 1;
int count = 0;
int num = 12;
String o = "O";
public boolean Example3() {
if (obj.equals(num)) return true;
// ok above, because single line IF statement is allowed in config.
if (true) {
count = 2;
} else
// ok above, because single line ELSE statement is allowed in config.
return false;
for (int i = 0; i < 5; i++) {
++count;}
do // violation, ''do' construct must use '{}'s.'
++count;
while (false);
for (int j = 0; j < 10; j++);
// ok above, because single line FOR statement is allowed in config.
for(int i = 0; i < 10; value.charAt(12));
// ok above, because single line FOR statement is allowed in config.
while (counter < 10)
// violation above, ''while' construct must use '{}'s.'
++count;
while (value.charAt(12) < 5);
// ok above, because single line FOR statement is allowed in config.
switch (num) {
case 1: counter++; break;
}
return true;
}
}
To configure the check to allow case, default single-line statements
without braces:
<module name="Checker">
<module name="TreeWalker">
<module name="NeedBraces">
<property name="tokens" value="LITERAL_CASE, LITERAL_DEFAULT"/>
<property name="allowSingleLineStatement" value="true"/>
</module>
</module>
</module>
Next statements won't be violated by check:
class Example4 {
String obj = new String();
String value = new String();
int counter = 1;
int count = 0;
int num = 12;
String o = "O";
public boolean Example4() {
if (obj.equals(num)) return true;
// ok above, because IF is not a target of validation
if (true) {
count = 2;
} else
// ok above, because ELSE is not a target of validation
return false;
for (int i = 0; i < 5; i++) {
++count;}
do // ok, because DO is not a target of validation
++count;
while (false);
for (int j = 0; j < 10; j++);
// ok above, because FOR is not a target of validation
for(int i = 0; i < 10; value.charAt(12));
// ok above, because FOR is not a target of validation
while (counter < 10)
// ok above, because WHILE is not a target of validation
++count;
while (value.charAt(12) < 5);
// ok above, because WHILE is not a target of validation
switch (num) {
case 1: counter++; break;
}
return true;
}
}
To configure the check to allow loops (while, for) with empty bodies:
<module name="Checker">
<module name="TreeWalker">
<module name="NeedBraces">
<property name="allowEmptyLoopBody" value="true"/>
<property name="tokens" value="LITERAL_WHILE, LITERAL_FOR"/>
</module>
</module>
</module>
Example:
class Example5 {
String obj = new String();
String value = new String();
int counter = 1;
int count = 0;
int num = 12;
String o = "O";
public boolean Example5() {
if (obj.equals(num)) return true;
// ok above, because IF is not a target of validation
if (true) {
count = 2;
} else
// ok above, because ELSE is not a target of validation
return false;
for (int i = 0; i < 5; i++) {
++count;}
do // ok, because DO is not a target of validation
++count;
while (false);
for (int j = 0; j < 10; j++);
// ok above, because FOR is not a target of validation
for(int i = 0; i < 10; value.charAt(12));
// ok above, because FOR is not a target of validation
while (counter < 10)
// violation above, ''while' construct must use '{}'s.'
++count;
while (value.charAt(12) < 5);
// ok above, because WHILE is not a target of validation
switch (num) {
case 1: counter++; break;
}
return true;
}
}
To configure the check to lambdas:
<module name="Checker">
<module name="TreeWalker">
<module name="NeedBraces">
<property name="tokens" value="LAMBDA"/>
<property name="allowSingleLineStatement" value="true"/>
</module>
</module>
</module>
Results in following:
class Example6 {
enum HttpMethod {GET, OPTIONS}
Object result = new Object();
private CustomCompletableFuture<Object> allowedFuture;
Example6() {
allowedFuture = new CustomCompletableFuture<>();
allowedFuture.addCallback(result -> assertEquals("Invalid response", // violation
EnumSet.of(HttpMethod.GET, HttpMethod.OPTIONS), result),
ex -> fail(ex.getMessage()));
allowedFuture.addCustomCallback(() -> {
return assertEquals("Invalid response",
EnumSet.of(HttpMethod.GET, HttpMethod.OPTIONS), result);},
ex -> fail(ex.getMessage()));}
private Object assertEquals(String invalidResponse, EnumSet<HttpMethod> get,
Object result) {
return result;}
private String fail(String message) {
return message;
}}
class CustomCompletableFuture<T> {
private CompletableFuture<T> allowedFuture;
public CustomCompletableFuture() {
allowedFuture = new CompletableFuture<>();
}
public void addCallback(java.util.function.Consumer<T> successCallback,
java.util.function.Consumer<Throwable> failureCallback) {}
public void addCustomCallback(java.util.function.Supplier<Object> successLambda,
java.util.function.Consumer<Throwable> failureLambda) {}
}
All messages can be customized if the default message doesn't suit you. Please see the documentation to learn how to.
com.puppycrawl.tools.checkstyle.checks.blocks