public class InnerAssignmentCheck extends AbstractCheck
Checks for assignments in subexpressions, such as in
String s = Integer.toString(i = 2);.
Rationale: With the exception of loop idioms, all assignments should occur in their own top-level statement to increase readability. With inner assignments like the one given above, it is difficult to see all places where a variable is set.
Note: Check allows usage of the popular assignments in loops:
String line;
while ((line = bufferedReader.readLine()) != null) { // OK
// process the line
}
for (;(line = bufferedReader.readLine()) != null;) { // OK
// process the line
}
do {
// process the line
}
while ((line = bufferedReader.readLine()) != null); // OK
Assignment inside a condition is not a problem here, as the assignment is surrounded
by an extra pair of parentheses. The comparison is != null and there is no chance that
intention was to write line == reader.readLine().
To configure the check:
<module name="InnerAssignment"/>
Example:
class MyClass {
void foo() {
int a, b;
a = b = 5; // violation, assignment to each variable should be in a separate statement
a = b += 5; // violation
a = 5; // OK
b = 5; // OK
a = 5; b = 5; // OK
double myDouble;
double[] doubleArray = new double[] {myDouble = 4.5, 15.5}; // violation
String nameOne;
List<String> myList = new ArrayList<String>();
myList.add(nameOne = "tom"); // violation
for (int k = 0; k < 10; k = k + 2) { // OK
// some code
}
boolean someVal;
if (someVal = true) { // violation
// some code
}
while (someVal = false) {} // violation
InputStream is = new FileInputStream("textFile.txt");
while ((b = is.read()) != -1) { // OK, this is a common idiom
// some code
}
}
boolean testMethod() {
boolean val;
return val = true; // violation
}
}
Parent is com.puppycrawl.tools.checkstyle.TreeWalker
Violation Message Keys:
assignment.inner.avoid
AutomaticBean.OutputStreamOptions| Modifier and Type | Field and Description |
|---|---|
private static int[][] |
ALLOWED_ASSIGNMENT_CONTEXT
List of allowed AST types from an assignment AST node
towards the root.
|
private static int[][] |
ALLOWED_ASSIGNMENT_IN_COMPARISON_CONTEXT
List of allowed AST types from a comparison node (above an assignment)
towards the root.
|
private static int[] |
COMPARISON_TYPES
The token types that identify comparison operators.
|
private static int[][] |
CONTROL_CONTEXT
List of allowed AST types from an assignment AST node
towards the root.
|
private static int[] |
LOOP_IDIOM_IGNORED_PARENTS
The token types that are ignored while checking "loop-idiom".
|
static java.lang.String |
MSG_KEY
A key is pointing to the warning message text in "messages.properties"
file.
|
| Constructor and Description |
|---|
InnerAssignmentCheck() |
| Modifier and Type | Method and Description |
|---|---|
int[] |
getAcceptableTokens()
The configurable token set.
|
int[] |
getDefaultTokens()
Returns the default token a check is interested in.
|
private static DetailAST |
getParent(DetailAST ast,
int... skipTokens)
Get ast parent, ignoring token types from
skipTokens. |
int[] |
getRequiredTokens()
The tokens that this check must be registered for.
|
private static boolean |
isComparison(DetailAST ast)
Checks if an AST is a comparison operator.
|
private static boolean |
isInContext(DetailAST ast,
int[][] contextSet,
int... skipTokens)
Tests whether the provided AST is in
one of the given contexts.
|
private static boolean |
isInLoopIdiom(DetailAST ast)
Tests whether the given AST is used in the "assignment in loop" idiom.
|
private static boolean |
isInNoBraceControlStatement(DetailAST ast)
Determines if ast is in the body of a flow control statement without
braces.
|
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
private static final int[][] ALLOWED_ASSIGNMENT_CONTEXT
private static final int[][] CONTROL_CONTEXT
private static final int[][] ALLOWED_ASSIGNMENT_IN_COMPARISON_CONTEXT
private static final int[] COMPARISON_TYPES
private static final int[] LOOP_IDIOM_IGNORED_PARENTS
public InnerAssignmentCheck()
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 isInNoBraceControlStatement(DetailAST ast)
if (y < 0)
x = y;
This leads to the following AST structure:
LITERAL_IF
LPAREN
EXPR // test
RPAREN
EXPR // body
SEMI
We need to ensure that ast is in the body and not in the test.
ast - an assignment operator ASTprivate static boolean isInLoopIdiom(DetailAST ast)
String line;
while ((line = bufferedReader.readLine()) != null) {
// process the line
}
for (;(line = bufferedReader.readLine()) != null;) {
// process the line
}
do {
// process the line
}
while ((line = bufferedReader.readLine()) != null);
Assignment inside a condition is not a problem here, as the assignment is surrounded by an
extra pair of parentheses. The comparison is != null and there is no chance that
intention was to write line == reader.readLine().ast - assignment ASTprivate static boolean isComparison(DetailAST ast)
ast - the AST to checkprivate static boolean isInContext(DetailAST ast, int[][] contextSet, int... skipTokens)
ast - the AST from which to start walking towards rootcontextSet - the contexts to test against.skipTokens - parent token types to ignoreCopyright © 2001-2022. All Rights Reserved.