diff --git a/.gitignore b/.gitignore
index 848d14da9..43716306e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -239,6 +239,7 @@ rt/test/save/ZSTRMAC2.[mM][lL][cC]
 **/*.[xX][lL][sS]
 **/*.[xX][lL][sS][xX]
 **/*.[xX][mM][lL]
+!src/**/*.[xX][mM][lL]
 
 # Backup and junk files
 macold/
diff --git a/bat/BLDJAR.BAT b/bat/BLDJAR.BAT
index bb8bae826..f1247c5b7 100644
--- a/bat/BLDJAR.BAT
+++ b/bat/BLDJAR.BAT
@@ -32,6 +32,16 @@ shift /1
 goto opt_loop
 :options_ok
 
+rem download linter jar
+if not exist "build\checkstyle"                    mkdir build\checkstyle
+if not exist "build\checkstyle\checkstyle-all.jar" powershell -NoProfile -ExecutionPolicy Bypass -File "bat\GetCheckStyle.ps1"
+if not exist "build\checkstyle\checkstyle-all.jar" goto return || rem download must have failed - cannot continue
+java -jar build\checkstyle\checkstyle-all.jar --version
+
+rem run the linter
+java -jar build\checkstyle\checkstyle-all.jar -c src\checkstyle.xml src
+if %ERRORLEVEL% NEQ 0 goto return
+
 rem prepare to compile java code and create jar file
 if not exist ".\jar\" mkdir jar
 cd jar
diff --git a/bat/GetCheckStyle.PS1 b/bat/GetCheckStyle.PS1
new file mode 100644
index 000000000..ef58cdd90
--- /dev/null
+++ b/bat/GetCheckStyle.PS1
@@ -0,0 +1,39 @@
+# Suppress Invoke-WebRequest's built-in progress bar
+$ProgressPreference = 'SilentlyContinue'
+
+# Request latest release information
+$apiUrl = 'https://api.github.com/repos/checkstyle/checkstyle/releases/latest'
+$release = Invoke-RestMethod -Uri $apiUrl -Headers @{ 'User-Agent' = 'z390-build' }
+
+# Tag is usually "checkstyle-13.4.2"
+$tag = $release.tag_name
+
+$asset = $release.assets | Where-Object { $_.name -match '-all\.jar$' } | Select-Object -First 1
+if (-not $asset) {
+    Write-Host "No -all.jar asset found for $tag" -ForegroundColor Red
+    exit 1
+}
+
+$uri     = $asset.browser_download_url
+$outFile = "build\checkstyle\checkstyle-all.jar"
+$versionFile = 'build\checkstyle\version.txt'
+
+# Issue status message
+Write-Host "Downloading linter from checkstyle repository on github.com..."
+
+# Define our own progress bar
+Write-Progress -Activity "Download" -Status $uri -PercentComplete 0
+
+# Download linter jar and report results
+try {
+    Invoke-WebRequest -Uri $uri -OutFile $outFile -UseBasicParsing
+    $tag | Set-Content -Path $versionFile -NoNewline
+    Write-Progress -Activity "Download" -Completed
+    Write-Host "Download finished: $tag"
+    exit 0
+}
+catch {
+    Write-Progress -Activity "Download" -Completed
+    Write-Host "Download failed: $($_.Exception.Message)" -ForegroundColor Red
+    exit 1
+}
\ No newline at end of file
diff --git a/src/az390.java b/src/az390.java
index c2c419fc5..85dd38152 100644
--- a/src/az390.java
+++ b/src/az390.java
@@ -20,8 +20,6 @@
 import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.File;
-import java.io.FileReader;
-import java.io.FileWriter;
 import java.io.RandomAccessFile;
 import java.lang.reflect.Array;
 import java.math.BigDecimal;
diff --git a/src/checkstyle.xml b/src/checkstyle.xml
new file mode 100644
index 000000000..47e8393d6
--- /dev/null
+++ b/src/checkstyle.xml
@@ -0,0 +1,83 @@
+<?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">
+  <!-- Disallow tabs for indentation -->
+  <module name="FileTabCharacter">
+    <property name="eachLine" value="true"/><!-- use true to report every tab -->
+    <property name="fileExtensions" value="java"/>
+  </module>
+
+  <!-- Disallow trailing whitespace -->
+  <module name="RegexpSingleline">
+    <property name="format" value="\s+$"/>
+    <property name="message" value="Line has trailing whitespace."/>
+    <property name="fileExtensions" value="java"/>
+  </module>
+
+  <module name="TreeWalker">
+    <!-- File name must match class definition -->
+    <module name="OuterTypeFilename"/>
+    <!-- Flag unused imports -->
+    <module name="UnusedImports"/>
+    <!-- Enforce indent of 4 spaces per nesting level -->
+    <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="4"/>
+      <property name="arrayInitIndent" value="4"/>
+    </module>
+    <!-- Three blank lines required before each class and method/function -->
+    <module name="EmptyLineSeparator">
+      <property name="tokens" value="CLASS_DEF, METHOD_DEF, CTOR_DEF"/>
+      <property name="allowNoEmptyLineBetweenFields" value="true"/><!-- Require at least one blank line -->
+      <property name="allowMultipleEmptyLines" value="true"/><!-- Allow more than one blank line -->
+    </module>
+    <!-- Open brace must be at end of a line -->
+    <module name="LeftCurly">
+      <property name="option" value="eol"/>
+    </module>
+    <module name="WhitespaceAround">
+      <property name="tokens" value="LCURLY"/>
+      <property name="allowEmptyMethods" value="false"/>
+      <property name="allowEmptyConstructors" value="true"/>
+      <property name="allowEmptyTypes" value="false"/>
+      <property name="allowEmptyLoops" value="false"/>
+      <property name="allowEmptyLambdas" value="false"/>
+      <property name="allowEmptyCatches" value="false"/>
+    </module>
+    <!-- Closing brace must be at proper indent -->
+    <module name="RightCurly">
+      <property name="option" value="same"/><!-- allow `} else {` -->
+    </module>
+    <!-- JavadocMethod allows more specific and stricter checks -->
+    <!--     For now, we'll use the two below checks -->
+    <!-- Require Javadoc on member fields (all access levels) -->
+    <module name="JavadocVariable">
+      <property name="accessModifiers" value="public, protected, package, private"/>
+    </module>
+    <!-- Require Javadoc on methods and constructors (all access levels) -->
+    <module name="MissingJavadocMethod">
+      <property name="scope" value="private"/>
+    </module>
+  </module>
+
+  <!-- In addition to EmptyLineSeparator above, require three blank lines as a class/method separator -->
+  <!-- Require three empty lines after `}` marker -->
+  <module name="RegexpMultiline">
+    <property name="matchAcrossLines" value="true"/>
+    <property name="format" value="(?m)\*/\r?\n(?:\r?\n){0,2}[ \t]*/\*\*\r?\n[ \t]*\*"/>
+    <property name="message" value="Need 3 empty lines before Javadoc (after '}')."/>
+    <property name="fileExtensions" value="java"/>
+  </module>
+  <!-- Require three empty lines after the last import -->
+  <module name="RegexpMultiline">
+    <property name="matchAcrossLines" value="true"/>
+    <property name="format" value="(?m)^import\s+[^;]+;\r?\n(?:\r?\n){0,2}[ \t]*/\*\*"/>
+    <property name="message" value="Need 3 empty lines before class Javadoc (after imports)."/>
+    <property name="fileExtensions" value="java"/>
+  </module>
+</module>
diff --git a/src/mz390.java b/src/mz390.java
index 1f3225333..0919a2f17 100644
--- a/src/mz390.java
+++ b/src/mz390.java
@@ -20,8 +20,6 @@
 import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.File;
-import java.io.FileReader;
-import java.io.FileWriter;
 import java.lang.reflect.Array;
 import java.text.SimpleDateFormat;
 import java.util.Arrays;