Customize Checkstyle

Checkstyle is one of java code review tool and is highly configurable.

One of the customized check is given below.

Check to find the usage of "+=" for String concatenation.
Below code checks for the usage of "+=" for String concatenation in the java file and reports the same.This is one of the most useful check which does not come with checkstyle_checks.xml.

Lets name the check as "StringConcatenationCheck".

import com.puppycrawl.tools.checkstyle.api.Check;

import com.puppycrawl.tools.checkstyle.api.DetailAST;

import com.puppycrawl.tools.checkstyle.api.TokenTypes;
public class StringConcatenationCheck extends Check{

/** Creates a new instance of StringConcatenationCheck */

public StringConcatenationCheck() { }

public int[] getDefaultTokens(){

return new int[]{

TokenTypes.PLUS_ASSIGN

}; }

public void visitToken(DetailAST plusAssignNode){

if(plusAssignNode.branchContains(TokenTypes.STRING_LITERAL))

log(plusAssignNode.getLineNo(),"stringusage.err.msg");

}}

Just add the name of the check in your checkstyle_checks.xml to use it.

Similarly we can write checks to check if database connections/streams are properly closed.

Let me know if anybody insterested in source code.