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

Class OneStatementPerLineCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable
    public final class OneStatementPerLineCheck
extends AbstractCheck
    Restricts the number of statements per line to one.

    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, assignment statements, expression statements, increment statements, object creation statements, 'for loop' statements, 'break' statements, 'continue' statements, 'return' statements, import statements.

    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

    • 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

      • countOfSemiInLambda

        private final java.util.Deque<java.lang.Integer> countOfSemiInLambda
        Counts number of semicolons in nested lambdas.

      • lastStatementEnd

        private int lastStatementEnd
        Hold the line-number where the last statement ended.

      • forStatementEnd

        private int forStatementEnd
        Hold the line-number where the last 'for-loop' statement ended.

      • inForHeader

        private boolean inForHeader
        The for-header usually has 3 statements on one line, but THIS IS OK.

      • isInLambda

        private boolean isInLambda
        Holds if current token is inside lambda.

      • lambdaStatementEnd

        private int lambdaStatementEnd
        Hold the line-number where the last lambda statement ended.

    • Constructor Detail

      • OneStatementPerLineCheck

        public OneStatementPerLineCheck()

    • Method Detail

      • 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

      • checkIfSemicolonIsInDifferentLineThanPrevious

        private void checkIfSemicolonIsInDifferentLineThanPrevious​(DetailAST ast)
        Checks if given semicolon is in different line than previous.
        Parameters:
        ast - semicolon to check

      • isOnTheSameLine

        private static boolean isOnTheSameLine​(DetailAST ast,
                                       int lastStatementEnd,
                                       int forStatementEnd,
                                       int lambdaStatementEnd)
        Checks whether two statements are on the same line.
        Parameters:
        ast - token for the current statement.
        lastStatementEnd - the line-number where the last statement ended.
        forStatementEnd - the line-number where the last 'for-loop' statement ended.
        lambdaStatementEnd - the line-number where the last lambda statement ended.
        Returns:
        true if two statements are on the same line.

      • isMultilineStatement

        private static boolean isMultilineStatement​(DetailAST ast)
        Checks whether statement is multiline.
        Parameters:
        ast - token for the current statement.
        Returns:
        true if one statement is distributed over two or more lines.