Class IndentationCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public class IndentationCheck
    extends AbstractCheck

    Checks correct indentation of Java code.

    The idea behind this is that while pretty printers are sometimes convenient for bulk reformats of legacy code, they often either aren't configurable enough or just can't anticipate how format should be done. Sometimes this is personal preference, other times it is practical experience. In any case, this check should just ensure that a minimal set of indentation rules is followed.

    Basic offset indentation is used for indentation inside code blocks. For any lines that span more than 1, line wrapping indentation is used for those lines after the first. Brace adjustment, case, and throws indentations are all used only if those specific identifiers start the line. If, for example, a brace is used in the middle of the line, its indentation will not take effect. All indentations have an accumulative/recursive effect when they are triggered. If during a line wrapping, another code block is found and it doesn't end on that same line, then the subsequent lines afterwards, in that new code block, are increased on top of the line wrap and any indentations above it.

    Example:

     if ((condition1 && condition2)
             || (condition3 && condition4)    // line wrap with bigger indentation
             ||!(condition5 && condition6)) { // line wrap with bigger indentation
       field.doSomething()                    // basic offset
           .doSomething()                     // line wrap
           .doSomething( c -> {               // line wrap
             return c.doSome();               // basic offset
           });
     }
     
    • Property basicOffset - Specify how far new indentation level should be indented when on the next line. Type is int. Default value is 4.
    • Property braceAdjustment - Specify how far a braces should be indented when on the next line. Type is int. Default value is 0.
    • Property caseIndent - Specify how far a case label should be indented when on next line. Type is int. Default value is 4.
    • Property throwsIndent - Specify how far a throws clause should be indented when on next line. Type is int. Default value is 4.
    • Property arrayInitIndent - Specify how far an array initialisation should be indented when on next line. Type is int. Default value is 4.
    • Property lineWrappingIndentation - Specify how far continuation line should be indented when line-wrapping is present. Type is int. Default value is 4.
    • Property forceStrictCondition - Force strict indent level in line wrapping case. If value is true, line wrap indent have to be same as lineWrappingIndentation parameter. If value is false, line wrap indent could be bigger on any value user would like. Type is boolean. Default value is false.

    To configure the default check:

     <module name="Indentation"/>
     

    Example of Compliant code for default configuration (in comment name of property that controls indentations):

     class Test {
        String field;               // basicOffset
        int[] arr = {               // basicOffset
            5,                      // arrayInitIndent
            6 };                    // arrayInitIndent
        void bar() throws Exception // basicOffset
        {                           // braceAdjustment
            foo();                  // basicOffset
        }                           // braceAdjustment
        void foo() {                // basicOffset
            if ((cond1 && cond2)    // basicOffset
                      || (cond3 && cond4)    // lineWrappingIndentation, forceStrictCondition
                      ||!(cond5 && cond6)) { // lineWrappingIndentation, forceStrictCondition
                field.doSomething()          // basicOffset
                    .doSomething()           // lineWrappingIndentation and forceStrictCondition
                    .doSomething( c -> {     // lineWrappingIndentation and forceStrictCondition
                        return c.doSome();   // basicOffset
                    });
            }
        }
        void fooCase()                // basicOffset
            throws Exception {        // throwsIndent
            switch (field) {          // basicOffset
                case "value" : bar(); // caseIndent
            }
        }
     }
     

    To configure the check to enforce the indentation style recommended by Oracle:

     <module name="Indentation">
       <property name="caseIndent" value="0"/>
     </module>
     

    Example of Compliant code for default configuration (in comment name of property that controls indentation):

     void fooCase() {          // basicOffset
         switch (field) {      // basicOffset
         case "value" : bar(); // caseIndent
         }
     }
     

    To configure the Check to enforce strict condition in line-wrapping validation.

     <module name="Indentation">
       <property name="forceStrictCondition" value="true"/>
     </module>
     

    Such config doesn't allow next cases even code is aligned further to the right for better reading:

     void foo(String aFooString,
             int aFooInt) { // indent:8 ; expected: 4; violation, because 8 != 4
         if (cond1
             || cond2) {
             field.doSomething()
                 .doSomething();
         }
         if ((cond1 && cond2)
                   || (cond3 && cond4)    // violation
                   ||!(cond5 && cond6)) { // violation
             field.doSomething()
                  .doSomething()          // violation
                  .doSomething( c -> {    // violation
                      return c.doSome();
                 });
         }
     }
     

    But if forceStrictCondition = false, this code is valid:

     void foo(String aFooString,
             int aFooInt) { // indent:8 ; expected: > 4; ok, because 8 > 4
         if (cond1
             || cond2) {
             field.doSomething()
                 .doSomething();
         }
         if ((cond1 && cond2)
                   || (cond3 && cond4)
                   ||!(cond5 && cond6)) {
             field.doSomething()
                  .doSomething()
                  .doSomething( c -> {
                      return c.doSome();
                 });
         }
     }
     

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • indentation.child.error
    • indentation.child.error.multi
    • indentation.error
    • indentation.error.multi
    Since:
    3.1
    • Method Detail

      • isForceStrictCondition

        public boolean isForceStrictCondition()
        Getter to query strict indent level in line wrapping case. If value is true, line wrap indent have to be same as lineWrappingIndentation parameter. If value is false, line wrap indent could be bigger on any value user would like.
        Returns:
        forceStrictCondition value.
      • setForceStrictCondition

        public void setForceStrictCondition​(boolean value)
        Setter to force strict indent level in line wrapping case. If value is true, line wrap indent have to be same as lineWrappingIndentation parameter. If value is false, line wrap indent could be bigger on any value user would like.
        Parameters:
        value - user's value of forceStrictCondition.
      • setBasicOffset

        public void setBasicOffset​(int basicOffset)
        Setter to specify how far new indentation level should be indented when on the next line.
        Parameters:
        basicOffset - the number of tabs or spaces to indent
      • getBasicOffset

        public int getBasicOffset()
        Getter to query how far new indentation level should be indented when on the next line.
        Returns:
        the number of tabs or spaces to indent
      • setBraceAdjustment

        public void setBraceAdjustment​(int adjustmentAmount)
        Setter to specify how far a braces should be indented when on the next line.
        Parameters:
        adjustmentAmount - the brace offset
      • getBraceAdjustment

        public int getBraceAdjustment()
        Getter to query how far a braces should be indented when on the next line.
        Returns:
        the positive offset to adjust braces
      • setCaseIndent

        public void setCaseIndent​(int amount)
        Setter to specify how far a case label should be indented when on next line.
        Parameters:
        amount - the case indentation level
      • getCaseIndent

        public int getCaseIndent()
        Getter to query how far a case label should be indented when on next line.
        Returns:
        the case indentation level
      • setThrowsIndent

        public void setThrowsIndent​(int throwsIndent)
        Setter to specify how far a throws clause should be indented when on next line.
        Parameters:
        throwsIndent - the throws indentation level
      • getThrowsIndent

        public int getThrowsIndent()
        Getter to query how far a throws clause should be indented when on next line.
        Returns:
        the throws indentation level
      • setArrayInitIndent

        public void setArrayInitIndent​(int arrayInitIndent)
        Setter to specify how far an array initialisation should be indented when on next line.
        Parameters:
        arrayInitIndent - the array initialisation indentation level
      • getArrayInitIndent

        public int getArrayInitIndent()
        Getter to query how far an array initialisation should be indented when on next line.
        Returns:
        the initialisation indentation level
      • getLineWrappingIndentation

        public int getLineWrappingIndentation()
        Getter to query how far continuation line should be indented when line-wrapping is present.
        Returns:
        the line-wrapping indentation level
      • setLineWrappingIndentation

        public void setLineWrappingIndentation​(int lineWrappingIndentation)
        Setter to specify how far continuation line should be indented when line-wrapping is present.
        Parameters:
        lineWrappingIndentation - the line-wrapping indentation level
      • indentationLog

        public void indentationLog​(DetailAST ast,
                                   String key,
                                   Object... args)
        Log a violation message.
        Parameters:
        ast - the ast for which error to be logged
        key - the message that describes the violation
        args - the details of the message
        See Also:
        MessageFormat
      • getIndentationTabWidth

        public int getIndentationTabWidth()
        Get the width of a tab.
        Returns:
        the width of a tab
      • 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
      • beginTree

        public void beginTree​(DetailAST ast)
        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:
        ast - the root of the tree