Package com.puppycrawl.tools.checkstyle.checks.coding

Class OneStatementPerLineCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable
    public final class OneStatementPerLineCheck
extends AbstractCheck

    Checks that there is only one statement per line.

    Rationale: It's very difficult to read multiple statements on one line.

    In the Java programming language, statements are the fundamental unit of execution. All statements except blocks are terminated by a semicolon. Blocks are denoted by open and close curly braces.

    OneStatementPerLineCheck checks the following types of statements: variable declaration statements, empty statements, import statements, assignment statements, expression statements, increment statements, object creation statements, 'for loop' statements, 'break' statements, 'continue' statements, 'return' statements, resources statements (optional).

    • Property treatTryResourcesAsStatement - Enable resources processing. Type is boolean. Default value is false.

    To configure the check: 

     <module name="OneStatementPerLine"/>

    The following examples will be flagged as a violation: 

     //Each line causes violation:
 int var1; int var2;
 var1 = 1; var2 = 2;
 int var1 = 1; int var2 = 2;
 var1++; var2++;
 Object obj1 = new Object(); Object obj2 = new Object();
 import java.io.EOFException; import java.io.BufferedReader;
 ;; //two empty statements on the same line.

 //Multi-line statements:
 int var1 = 1
 ; var2 = 2; //violation here
 int o = 1, p = 2,
 r = 5; int t; //violation here

    An example of how to configure the check to treat resources in a try statement as statements to require them on their own line: 

     <module name="OneStatementPerLine">
   <property name="treatTryResourcesAsStatement" value="true"/>
 </module>

    Note: resource declarations can contain variable definitions and variable references (from java9). When property "treatTryResourcesAsStatement" is enabled, this check is only applied to variable definitions. If there are one or more variable references and one variable definition on the same line in resources declaration, there is no violation. The following examples will illustrate difference: 

     OutputStream s1 = new PipedOutputStream();
 OutputStream s2 = new PipedOutputStream();
 // only one statement(variable definition) with two variable references
 try (s1; s2; OutputStream s3 = new PipedOutputStream();) // OK
 {}
 // two statements with variable definitions
 try (Reader r = new PipedReader(); s2; Reader s3 = new PipedReader() // violation
 ) {}

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • multiple.statements.line
    Since:
    5.3

    • Field Detail

      • MSG_KEY

        public static final java.lang.String MSG_KEY
        A key is pointing to the warning message text in "messages.properties" file.
        See Also:
        Constant Field Values

    • Constructor Detail

      • OneStatementPerLineCheck

        public OneStatementPerLineCheck()

    • Method Detail

      • setTreatTryResourcesAsStatement

        public void setTreatTryResourcesAsStatement​(boolean treatTryResourcesAsStatement)
        Setter to enable resources processing.
        Parameters:
        treatTryResourcesAsStatement - user's value of treatTryResourcesAsStatement.

      • getDefaultTokens

        public int[] getDefaultTokens()
        Description copied from class: AbstractCheck
        Returns the default token a check is interested in. Only used if the configuration for a check does not define the tokens.
        Specified by:
        getDefaultTokens in class AbstractCheck
        Returns:
        the default tokens
        See Also:
        TokenTypes

      • getAcceptableTokens

        public int[] getAcceptableTokens()
        Description copied from class: AbstractCheck
        The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.
        Specified by:
        getAcceptableTokens in class AbstractCheck
        Returns:
        the token set this check is designed for.
        See Also:
        TokenTypes

      • getRequiredTokens

        public int[] getRequiredTokens()
        Description copied from class: AbstractCheck
        The tokens that this check must be registered for.
        Specified by:
        getRequiredTokens in class AbstractCheck
        Returns:
        the token set this must be registered for.
        See Also:
        TokenTypes

      • beginTree

        public void beginTree​(DetailAST rootAST)
        Description copied from class: AbstractCheck
        Called before the starting to process a tree. Ideal place to initialize information that is to be collected whilst processing a tree.
        Overrides:
        beginTree in class AbstractCheck
        Parameters:
        rootAST - the root of the tree

      • leaveToken

        public void leaveToken​(DetailAST ast)
        Description copied from class: AbstractCheck
        Called after all the child nodes have been process.
        Overrides:
        leaveToken in class AbstractCheck
        Parameters:
        ast - the token leaving