checkstyle.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
    "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
    "https://checkstyle.org/dtds/configuration_1_3.dtd">

<module name="Checker">
    <property name="severity" value="error"/>
    <property name="charset" value="UTF-8"/>

    <!-- No tab characters -->
    <module name="FileTabCharacter"/>

    <!-- Line length: 80 characters -->
    <module name="LineLength">
        <property name="max" value="80"/>
        <property name="ignorePattern"
                  value="^package.*|^import.*|a href|href|http://|https://|static final.*&lt;.*&gt;"/>
    </module>

    <!-- Allow CSOFF/CSON comments to suppress checks on specific lines -->
    <module name="SuppressWithPlainTextCommentFilter">
        <property name="offCommentFormat" value="CSOFF"/>
        <property name="onCommentFormat" value="CSON"/>
    </module>

    <module name="TreeWalker">

        <!-- Require braces, but allow single-line statements -->
        <module name="NeedBraces">
            <property name="allowSingleLineStatement" value="true"/>
        </module>

        <!-- Left curly brace placement is not enforced by checkstyle.
             Use same-line or next-line as appropriate for readability. -->

        <!-- Right curly brace: alone or followed by else/catch/finally -->
        <module name="RightCurly">
            <property name="option" value="alone_or_singleline"/>
            <property name="tokens" value="CLASS_DEF, METHOD_DEF, CTOR_DEF,
                LITERAL_FOR, LITERAL_WHILE, STATIC_INIT,
                INSTANCE_INIT, ANNOTATION_DEF, ENUM_DEF, INTERFACE_DEF,
                RECORD_DEF, COMPACT_CTOR_DEF"/>
        </module>
        <module name="RightCurly">
            <property name="option" value="same"/>
            <property name="tokens" value="LITERAL_TRY, LITERAL_CATCH,
                LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE,
                LITERAL_DO"/>
        </module>

        <!-- Indentation -->
        <module name="Indentation">
            <property name="basicOffset" value="4"/>
            <property name="braceAdjustment" value="0"/>
            <property name="caseIndent" value="0"/>
            <property name="throwsIndent" value="4"/>
            <property name="lineWrappingIndentation" value="8"/>
        </module>

        <!-- Operators wrap to beginning of next line -->
        <module name="OperatorWrap">
            <property name="option" value="nl"/>
        </module>

    </module>
</module>