public class MissingSwitchDefaultCheck extends AbstractCheck
Checks that switch statement has a default clause.
Rationale: It's usually a good idea to introduce a default case in every switch statement. Even if the developer is sure that all currently possible cases are covered, this should be expressed in the default branch, e.g. by using an assertion. This way the code is protected against later changes, e.g. introduction of new types in an enumeration type.
This check does not validate any switch expressions. Rationale: The compiler requires switch expressions to be exhaustive. This means that all possible inputs must be covered.
This check does not validate switch statements that use pattern or null labels. Rationale: Switch statements that use pattern or null labels are checked by the compiler for exhaustiveness. This means that all possible inputs must be covered.
See the Java Language Specification for more information about switch statements and expressions.
To configure the check:
<module name="MissingSwitchDefault"/>
Example of violation:
switch (i) { // violation
case 1:
break;
case 2:
break;
}
Example of correct code:
switch (i) {
case 1:
break;
case 2:
break;
default: // OK
break;
}
switch (o) {
case String s: // type pattern
System.out.println(s);
break;
case Integer i: // type pattern
System.out.println("Integer");
break;
default: // will not compile without default label, thanks to type pattern label usage
break;
}
Example of correct code which does not require default labels:
sealed interface S permits A, B, C {}
final class A implements S {}
final class B implements S {}
record C(int i) implements S {} // Implicitly final
/**
* The completeness of a switch statement can be
* determined by the contents of the permits clause
* of interface S. No default label or default case
* label is allowed by the compiler in this situation, so
* this check does not enforce a default label in such
* statements.
*/
static void showSealedCompleteness(S s) {
switch (s) {
case A a: System.out.println("A"); break;
case B b: System.out.println("B"); break;
case C c: System.out.println("C"); break;
}
}
/**
* A total type pattern matches all possible inputs,
* including null. A default label or
* default case is not allowed by the compiler in this
* situation. Accordingly, check does not enforce a
* default label in this case.
*/
static void showTotality(String s) {
switch (s) {
case Object o: // total type pattern
System.out.println("o!");
}
}
enum Color { RED, GREEN, BLUE }
static int showSwitchExpressionExhaustiveness(Color color) {
switch (color) {
case RED: System.out.println("RED"); break;
case BLUE: System.out.println("BLUE"); break;
case GREEN: System.out.println("GREEN"); break;
// Check will require default label below, compiler
// does not enforce a switch statement with constants
// to be complete.
default: System.out.println("Something else");
}
// Check will not require default label in switch
// expression below, because code will not compile
// if all possible values are not handled. If the
// 'Color' enum is extended, code will fail to compile.
return switch (color) {
case RED:
yield 1;
case GREEN:
yield 2;
case BLUE:
yield 3;
};
}
Parent is com.puppycrawl.tools.checkstyle.TreeWalker
Violation Message Keys:
missing.switch.default
AutomaticBean.OutputStreamOptions| Modifier and Type | Field and Description |
|---|---|
static java.lang.String |
MSG_KEY
A key is pointing to the warning message text in "messages.properties"
file.
|
| Constructor and Description |
|---|
MissingSwitchDefaultCheck() |
| Modifier and Type | Method and Description |
|---|---|
private static boolean |
containsDefaultCaseLabelElement(DetailAST detailAst)
Checks if a switch block contains a default case label.
|
private static boolean |
containsDefaultLabel(DetailAST detailAst)
Checks if the case group or its sibling contain the 'default' switch.
|
private static boolean |
containsPatternCaseLabelElement(DetailAST detailAst)
Checks if a switch block contains a case label with a pattern variable definition.
|
int[] |
getAcceptableTokens()
The configurable token set.
|
int[] |
getDefaultTokens()
Returns the default token a check is interested in.
|
int[] |
getRequiredTokens()
The tokens that this check must be registered for.
|
private static boolean |
isSwitchExpression(DetailAST ast)
Checks if this LITERAL_SWITCH token is part of a switch expression.
|
void |
visitToken(DetailAST ast)
Called to process a token.
|
beginTree, clearViolations, destroy, finishTree, getFileContents, getLine, getLineCodePoints, getLines, getTabWidth, getTokenNames, getViolations, init, isCommentNodesRequired, leaveToken, log, log, log, setFileContents, setTabWidth, setTokensfinishLocalSetup, getCustomMessages, getId, getMessageBundle, getSeverity, getSeverityLevel, setId, setSeverityconfigure, contextualize, getConfiguration, setupChildpublic static final java.lang.String MSG_KEY
public MissingSwitchDefaultCheck()
public int[] getDefaultTokens()
AbstractCheckgetDefaultTokens in class AbstractCheckTokenTypespublic int[] getAcceptableTokens()
AbstractCheckgetAcceptableTokens in class AbstractCheckTokenTypespublic int[] getRequiredTokens()
AbstractCheckgetRequiredTokens in class AbstractCheckTokenTypespublic void visitToken(DetailAST ast)
AbstractCheckvisitToken in class AbstractCheckast - the token to processprivate static boolean containsDefaultLabel(DetailAST detailAst)
detailAst - first case group to check.private static boolean containsPatternCaseLabelElement(DetailAST detailAst)
detailAst - first case group to check.private static boolean containsDefaultCaseLabelElement(DetailAST detailAst)
detailAst - first case group to check.private static boolean isSwitchExpression(DetailAST ast)
ast - the switch statement we are checkingCopyright © 2001-2022. All Rights Reserved.