We Keep Coding

Java Spark GroupByFailure

I'm attempting to use the Java Spark libraries with a cluster running Spark 2.3.0 over Hadoop 3.1.0 (and using those versions of the Java libraries).
I've run into a problem where I simply cannot use groupByKey, and I am at a loss to explain why. Any attempted usage of groupByKey for any reason in any circumstance is returning a java.lang.IllegalArgumentException.
I've boiled this down to about the simplest test I can think of:
package com.failuretest;
import java.util.ArrayList;
import java.util.List;
import org.apache.spark.SparkConf;
import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.api.java.JavaSparkContext;
import scala.Tuple2;
public class TestReport {
public static void main(String[] args) throws Exception {
SparkConf conf = new SparkConf().setAppName("TestReport").set("spark.executor.memory", "20G");
JavaSparkContext sc = new JavaSparkContext(conf);
JavaRDD<String> test = sc.parallelize(generateTestData());
test.saveAsTextFile("/TEST/testfile1");
test.mapToPair(line -> {
String[] testParts = line.split(" ");
return new Tuple2<String, String>(testParts[0], testParts[1]);
}).groupByKey().saveAsTextFile("/TEST/testfile2");
sc.close();
}
private static List<String> generateTestData() {
List<String> testList = new ArrayList<String>();
int keyCount = 0;
int valCount = 0;
while (valCount++ < 2000000) {
if (valCount % 10 == 0) {
keyCount++;
}
testList.add("Key" + keyCount + " " + "Val" + valCount);
}
return testList;
}
}
I'm just programmatically creating an RDD that produces 10 values per key, then creating my JavaPairRDD with a simple split, then attempting groupByKey.
When it runs, I receive the following stack:
Exception in thread "main" java.lang.IllegalArgumentException
at org.apache.xbean.asm5.ClassReader.<init>(Unknown Source)
at org.apache.xbean.asm5.ClassReader.<init>(Unknown Source)
at org.apache.xbean.asm5.ClassReader.<init>(Unknown Source)
at org.apache.spark.util.ClosureCleaner$.getClassReader(ClosureCleaner.scala:46)
at org.apache.spark.util.FieldAccessFinder$$anon$3$$anonfun$visitMethodInsn$2.apply(ClosureCleaner.scala:449)
at org.apache.spark.util.FieldAccessFinder$$anon$3$$anonfun$visitMethodInsn$2.apply(ClosureCleaner.scala:432)
at scala.collection.TraversableLike$WithFilter$$anonfun$foreach$1.apply(TraversableLike.scala:733)
at scala.collection.mutable.HashMap$$anon$1$$anonfun$foreach$2.apply(HashMap.scala:103)
at scala.collection.mutable.HashMap$$anon$1$$anonfun$foreach$2.apply(HashMap.scala:103)
at scala.collection.mutable.HashTable$class.foreachEntry(HashTable.scala:230)
at scala.collection.mutable.HashMap.foreachEntry(HashMap.scala:40)
at scala.collection.mutable.HashMap$$anon$1.foreach(HashMap.scala:103)
at scala.collection.TraversableLike$WithFilter.foreach(TraversableLike.scala:732)
at org.apache.spark.util.FieldAccessFinder$$anon$3.visitMethodInsn(ClosureCleaner.scala:432)
at org.apache.xbean.asm5.ClassReader.a(Unknown Source)
at org.apache.xbean.asm5.ClassReader.b(Unknown Source)
at org.apache.xbean.asm5.ClassReader.accept(Unknown Source)
at org.apache.xbean.asm5.ClassReader.accept(Unknown Source)
at org.apache.spark.util.ClosureCleaner$$anonfun$org$apache$spark$util$ClosureCleaner$$clean$14.apply(ClosureCleaner.scala:262)
at org.apache.spark.util.ClosureCleaner$$anonfun$org$apache$spark$util$ClosureCleaner$$clean$14.apply(ClosureCleaner.scala:261)
at scala.collection.immutable.List.foreach(List.scala:381)
at org.apache.spark.util.ClosureCleaner$.org$apache$spark$util$ClosureCleaner$$clean(ClosureCleaner.scala:261)
at org.apache.spark.util.ClosureCleaner$.clean(ClosureCleaner.scala:159)
at org.apache.spark.SparkContext.clean(SparkContext.scala:2292)
at org.apache.spark.rdd.PairRDDFunctions$$anonfun$combineByKeyWithClassTag$1.apply(PairRDDFunctions.scala:88)
at org.apache.spark.rdd.PairRDDFunctions$$anonfun$combineByKeyWithClassTag$1.apply(PairRDDFunctions.scala:77)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112)
at org.apache.spark.rdd.RDD.withScope(RDD.scala:363)
at org.apache.spark.rdd.PairRDDFunctions.combineByKeyWithClassTag(PairRDDFunctions.scala:77)
at org.apache.spark.rdd.PairRDDFunctions$$anonfun$groupByKey$1.apply(PairRDDFunctions.scala:505)
at org.apache.spark.rdd.PairRDDFunctions$$anonfun$groupByKey$1.apply(PairRDDFunctions.scala:498)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112)
at org.apache.spark.rdd.RDD.withScope(RDD.scala:363)
at org.apache.spark.rdd.PairRDDFunctions.groupByKey(PairRDDFunctions.scala:498)
at org.apache.spark.rdd.PairRDDFunctions$$anonfun$groupByKey$3.apply(PairRDDFunctions.scala:641)
at org.apache.spark.rdd.PairRDDFunctions$$anonfun$groupByKey$3.apply(PairRDDFunctions.scala:641)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112)
at org.apache.spark.rdd.RDD.withScope(RDD.scala:363)
at org.apache.spark.rdd.PairRDDFunctions.groupByKey(PairRDDFunctions.scala:640)
at org.apache.spark.api.java.JavaPairRDD.groupByKey(JavaPairRDD.scala:559)
at com.failuretest.TestReport.main(TestReport.java:22)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at org.apache.spark.deploy.JavaMainApplication.start(SparkApplication.scala:52)
at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:879)
at org.apache.spark.deploy.SparkSubmit$.doRunMain$1(SparkSubmit.scala:197)
at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:227)
at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:136)
at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)
It doesn't get any further than the groupByKey (I'm writing a file above with the results, but it really doesn't matter since it never gets there).
I can run it all day long in my local dev instance, but running spark-submit with a jar containing the above fails every time in the cluster.
I'm really not sure where to go from here - what I am trying to do is a bit of a challenge if I cannot group by key.
Am I messing up? Is this a version conflict somewhere?
Dave

I actually figured this out before posting this, but in the interests of helping others...
I discovered that one of my colleagues had decided to have a play around with Java 10 on this particular cluster. Moved it back to Java 8 (sorry - didn't try 9) and the problem went away.
Dave

CSVhelper writeLine, null pointer halfway during a for-loop

For a java simulation project I have a log file that keeps track of everything that happens during a single run. I do this by adding objects of a custom TimeLog.class to a List. When the simulation is complete I loop through this list and write an ArrayList of strings for each entry, followed by writing it to a csv file using the following "CSVHelper" class which I found online (credits to Keke Chen).
Creating ArrayList of strings:
public static void saveData(List<TimeLog> data, String fileName, Simulator simulator,
ArrayList<String> header) throws Exception {
File csvFile = new File(simulator.getOutputFolder()+fileName);
FileOutputStream fos = new FileOutputStream(csvFile);
Writer fw = new OutputStreamWriter(fos, "UTF-8");
CSVHelper.writeLine(fw, header);
for (TimeLog entry : data) {
ArrayList<String> row = new ArrayList<>();
row.add(String.valueOf(entry.getTime())); //time of entry, double
row.add(String.valueOf(entry.getMessageType())); //type of message (SETUP, DEBUG, EVENT, ERROR)
if (entry.getEvent() == null) {
row.add("");
} else {
row.add(entry.getEvent().getTypeName()); //event type if event
}
row.add(entry.getLog()); //message
CSVHelper.writeLine(fw, row);
}
fw.flush();
fw.close();
}
CSVHelper.writeLine :
/** Class for processing csv file.
* created by Keke Chen (keke.chen#wright.edu)
* For Cloud Computing Labs
* Feb. 2014
*/
public static void writeLine(Writer w, ArrayList<String> values) throws Exception {
boolean firstVal = true;
for (String val : values) {
if (!firstVal) {
w.write(",");
}
w.write("\"");
for (int i=0; i<val.length(); i++) {
char ch = val.charAt(i);
if (ch=='\"') {
w.write("\""); //extra quote
}
w.write(ch);
}
w.write("\"");
firstVal = false;
}
w.write("\n");
}
For debugging purposes, I catch exceptions thrown by the simulator, add information about them to my logging list, write the log file, and then throw the exception again. This way, when a problem occurs I can look in the log file what happened.
Until recently this worked just fine, but now I get a NullPointerException during the 2nd for-loop in the writing process. For some reason the line
for (int i=0; i<val.length(); i++)
throws an exception halfway during a string. If I open the log file that is created, the last entry has a half finished message or timestamp as well (for example: "tool X was res" instead of "tool X was reserved for item Y" or "212" instead of "212312.16").
Is there any limitation to writing csv files, keeping lists in java, using for-loops on characters of strings, or anything else that I am not aware of? This is giving me quiet the headache.
Ciao,
Robin
EDIT: As requested, an example of the list entries:
//initiating:
private List<TimeLog> logging = new ArrayList<>();
//message:
public void message(MessageType mt, String s, Event e) {
if (saveLog) {
logFile.add(new TimeLog(now(), mt, s, e)); //now() gets the current time of the simulator
}
}
//example:
Event e = new ReservationEvent(simulator.now(), X, Y);
simulator.message(MessageType.EVENT, "Tool "+X.getId()+" was reserved for item "+Y+getId(), e);
this is the stack trace:
java.lang.NullPointerException
at model.simulator.transport.input.CSVHelper.writeLine(CSVHelper.java:27)
at model.simulator.TimeLog.saveData(TimeLog.java:73)
at model.simulator.Simulator.endSimulation(Simulator.java:98)
at model.simulator.Simulator.runSimulation(Simulator.java:64)
at test.simulator.compare.TestFullFab.testRunning(TestFullFab.java:147)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:539)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:761)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:461)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:207)
Something else that I noticed due to Emax's comment. I added
System.out.println("0:"+row.get(0)+", 1:"+row.get(1)+", 2:"+row.get(2)+", 3:"+row.get(3));
in the saveData method, just before CSVHelper.writeLine(fw,row), to see the list of strings before they get written. This resulted in the full list of logs in the console, so also the ones that did not (or partly) get written to the csv-file. Somehow, the TimeLog for-loop continues while the writeLine is throwing exceptions.
EDIT2: structure of TimeLog:
public class TimeLog {
private double time;
private MessageType mt;
private String log;
private Event e;
public TimeLog(double time, MessageType mt, String log, Event e) {
this.time = time;
this.mt = mt;
this.log = log;
this.e = e;
}
//see full method above
public static void saveData(List<TimeLog> data, String fileName, Simulator simulator,
ArrayList<String> header) throws Exception { ...
//further more, there are some getters
}
An example of the output in the console as a result of the System.out.println() line:
0:27131.490112666303, 1:EVENT, 2:TOOLEVENT, 3:Tool input event, item 3998 has gone into tool QSD301
keep in mind that the 0:,1:,2:, and 3: are not in the original list but added in the println() method.
UPDATE: Using Emax's idea of printing the values where it returns null revealed the problem. The value of val indeed becomes null, and it happens at the NullPointerException (which has no message), so e.getMessage() returns null. Strangly enough, the Writer simply does not write all the values in the csv file, but seems to have some kind of delay (maybe it first collects a default number of characters before actually writing it to the file or something?). Because of this, I thought the NullPointer happened during a loop through val, while it had already finished. Thanks for the help!

The only possible reason that cause a NullPointerException on that line is that val is null since val is taken from a list, the problem bubble up to:
row.add(String.valueOf(entry.getTime()));
row.add(String.valueOf(entry.getMessageType()));
row.add(entry.getEvent().getTypeName());
row.add(entry.getLog());
One of this add is adding a null to the list, you should check for one of this.
However post the full stracktrace including (if present) the "Caused By"
UPDATE
Try to modify writeLine like this:
[...]
if (!firstVal) {
w.write(",");
}
w.write("\"");
// EDIT HERE
if (val == null) {
System.out.println("This val is null: " + values);
}
// .....
for (int i = 0; i < val.length(); i++) {
[...]
Post the output with the case that caused the NullPointerException

How to load HashMap properly from a .yml file?

I am trying to load a HashMap from the config file using the standard Bukkit configuration files API.
HashMap:
public static HashMap<String, String> banned = new HashMap<String, String>();
This is the way I am trying to get the data:
public static boolean isBanned(String uuid) {
if (Dogends.config.getConfigurationSection("Banned").getKeys(true).contains(uuid)) {
return true;
}
return false;
}
If the player is banned then it's ok, but when the player is not banned, then it throws a NullPointerException out.
NullPointerException:
Could not pass event PlayerLoginEvent to Dogends v1.0
org.bukkit.event.EventException
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:302) ~[cb.jar:git-Bukkit-880a532]
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[cb.jar:git-Bukkit-880a532]
at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:501) [cb.jar:git-Bukkit-880a532]
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:486) [cb.jar:git-Bukkit-880a532]
at net.minecraft.server.v1_8_R3.PlayerList.attemptLogin(PlayerList.java:439) [cb.jar:git-Bukkit-880a532]
at net.minecraft.server.v1_8_R3.LoginListener.b(LoginListener.java:89) [cb.jar:git-Bukkit-880a532]
at net.minecraft.server.v1_8_R3.LoginListener.c(LoginListener.java:53) [cb.jar:git-Bukkit-880a532]
at net.minecraft.server.v1_8_R3.NetworkManager.a(NetworkManager.java:222) [cb.jar:git-Bukkit-880a532]
at net.minecraft.server.v1_8_R3.ServerConnection.c(SourceFile:168) [cb.jar:git-Bukkit-880a532]
at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:744) [cb.jar:git-Bukkit-880a532]
at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:335) [cb.jar:git-Bukkit-880a532]
at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:628) [cb.jar:git-Bukkit-880a532]
at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:536) [cb.jar:git-Bukkit-880a532]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_91]
Caused by: java.lang.NullPointerException
at me.woulfiee.server.ban.BanCommand.isBanned(BanCommand.java:47) ~[?:?]
at me.woulfiee.server.ban.BanCommand.onPlayerLogin(BanCommand.java:103) ~[?:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_91]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_91]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_91]
at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_91]
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:300) ~[cb.jar:git-Bukkit-880a532]
... 13 more
config.yml:
Ranks:
Player:
Players: []
Mythic:
Players: []
Doge:
Players: []
Youtuber:
Players: []
Builder:
Players: []
Mod:
Players: []
Admin:
Players: []
Owner:
Players:
- d166739c-32d3-4b37-a1be-883be57d736c
Broadcast:
Interval: 120
Banned:
d166739c-32d3-4b37-a1be-883be57d736c: "CONSOLE \xa7eHELP"

To accomplish what you wish, you should try the following:
Make sure your config is not null/exists
boolean isBanned(String uuid) {
FileConfiguration yourConfig;
//Getting the Banned section
ConfigurationSection banned = yourConfig.getConfigurationSection("Banned");
//All the keys inside the banned configuration section
Set<String> keys = banned.getKeys(false); //We don't want it to be deep
if (keys.contains(uuid))return true; //UUID is on the keys list, so the player is banned
return false; //UUID is not on the keys list, so the player is not banned
}
I don't believe you actually need the hashmap, unless you're using it for something else

getConfigurationSection:
If the ConfigurationSection does not exist but a default value has
been specified, this will return the default value. If the
ConfigurationSection does not exist and no default value was
specified, this will return null.
I'm guessing if there are no users banned, there is no Banned section, so getConfigurationSection returns null, which is why your getKeys() call throws a NPE.
So you should first check if the configuration section exists, and only then try to use it.

JClouds-Chef BootstrapConfig Builder MissingMethodException

Please note: although this question involve the JClouds-Chef library and Groovy here, I think this is a Java API question at heart.
On JClouds-Chef 1.7.3 here:
List<String> runlist = new RunListBuilder().addRole("typicalapp").build();
ArrayList<String> runList2 = new ArrayList<String>();
for(String item : runlist) {
runList2.add(item);
}
System.out.println("runList2 is of type: " + runList2.getClass().getName());
BootstrapConfig bootstrapConfig = BootstrapConfig.builder().runlist(runList2).build();
Produces the following output/exception:
runList2 is of type: java.util.ArrayList
Exception in thread "main" groovy.lang.MissingMethodException: No signature of method: org.jclouds.chef.domain.BootstrapConfig$Builder.runlist() is applicable for argument types: (java.util.ArrayList) values: [[role[typicalapp]]]
Possible solutions: runList(java.lang.Iterable), build(), split(groovy.lang.Closure)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:55)
at org.codehaus.groovy.runtime.callsite.PojoMetaClassSite.call(PojoMetaClassSite.java:46)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
at net.myuser.chef.test.ChefPlugin.provision(ChefPlugin.groovy:71)
at net.myuser.chef.test.ChefPlugin$provision.call(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:112)
at net.myuser.chef.test.ChefPlugin.main(ChefPlugin.groovy:27)
I'm pretty sure the code for this version of BootstrapConfig#Builder is here. As far as I can tell, ArrayList extends Iterable, so I can't see what's going on here.

You are using runlist instead of runList

Conditional formatting using in Excel using APACHE POI

I have a problem using the SheetConditionalFormatting, just for testing if the cell contains particular string (in my case just "test") I run the following code:
SheetConditionalFormatting sheetConditionalFormatting = excelSheet.getSheetConditionalFormatting();
ConditionalFormattingRule rule = sheetConditionalFormatting.createConditionalFormattingRule(ComparisonOperator.EQUAL, "test");
PatternFormatting fill1 = rule.createPatternFormatting();
fill1.setFillBackgroundColor(IndexedColors.BLUE.index);
fill1.setFillPattern(PatternFormatting.SOLID_FOREGROUND);
CellRangeAddress[] regions = {
CellRangeAddress.valueOf("A1")
};
sheetConditionalFormatting.addConditionalFormatting(regions, rule);
And I got message that 'test' does not exist in the workspace. This is my error from Console:
Exception in thread "main" org.apache.poi.ss.formula.FormulaParseException: Specified named range 'test' does not exist in the current workbook.
at org.apache.poi.ss.formula.FormulaParser.parseNonRange(FormulaParser.java:569)
at org.apache.poi.ss.formula.FormulaParser.parseRangeable(FormulaParser.java:429)
at org.apache.poi.ss.formula.FormulaParser.parseRangeExpression(FormulaParser.java:268)
at org.apache.poi.ss.formula.FormulaParser.parseSimpleFactor(FormulaParser.java:1119)
at org.apache.poi.ss.formula.FormulaParser.percentFactor(FormulaParser.java:1079)
at org.apache.poi.ss.formula.FormulaParser.powerFactor(FormulaParser.java:1066)
at org.apache.poi.ss.formula.FormulaParser.Term(FormulaParser.java:1426)
at org.apache.poi.ss.formula.FormulaParser.additiveExpression(FormulaParser.java:1526)
at org.apache.poi.ss.formula.FormulaParser.concatExpression(FormulaParser.java:1510)
at org.apache.poi.ss.formula.FormulaParser.comparisonExpression(FormulaParser.java:1467)
at org.apache.poi.ss.formula.FormulaParser.unionExpression(FormulaParser.java:1447)
at org.apache.poi.ss.formula.FormulaParser.parse(FormulaParser.java:1568)
at org.apache.poi.ss.formula.FormulaParser.parse(FormulaParser.java:176)
at org.apache.poi.hssf.model.HSSFFormulaParser.parse(HSSFFormulaParser.java:70)
at org.apache.poi.hssf.record.CFRuleRecord.parseFormula(CFRuleRecord.java:525)
at org.apache.poi.hssf.record.CFRuleRecord.create(CFRuleRecord.java:146)
at org.apache.poi.hssf.usermodel.HSSFSheetConditionalFormatting.createConditionalFormattingRule(HSSFSheetConditionalFormatting.java:80)
at org.apache.poi.hssf.usermodel.HSSFSheetConditionalFormatting.createConditionalFormattingRule(HSSFSheetConditionalFormatting.java:32)
at MainApp.main(MainApp.java:26)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)

it found out that string introduced into the createConditionalFormattingRule must be cell coordinates
ConditionalFormattingRule rule = sheetConditionalFormatting.createConditionalFormattingRule(ComparisonOperator.EQUAL, "B1");

To use a string as a comparison it need to be inclosed in quotes eg:
"""string"""