We Keep Coding

the stackTraceElement shows error in a function does not exist in my code

i created my own way to send all errors to the firebase realtime database, i send the activity name, function name, error message, error line number. but sometimes the stackTraceElement
send something like that "[myPackageName].MainActivity.B(Unknown Source:11)"
package name
activityName = MainActivity
function name = B (i dont have any function called B in all activities and classes)
error line number = 11 (on the line code 11, there is just an import of a static variable)
i wrote all function's code within try and catch
ex:
private void function_1(){
try{
//some code
}catch (Exception e) {
//getting the function name
String functionName = Objects.requireNonNull(new Object() {
}.getClass().getEnclosingMethod()).getName();
//getting the stackTraceElement that contains my acticityName
String stackTraceElement = "";
for (StackTraceElement ste : e.getStackTrace()) {
if (ste.getClassName().contains(activityName)) {
stackTraceElement = ste.toString();
break;
}
}
// getting the error message
String msg = e.getMessage();
//send all data to firebase through external class
fireBase_class.sendError(context, activityName, stackTraceElement, msg, functionName);
}
}
}
where the function B comes from? Note: some time i got function called M, N, L, A .....
also, if anyone have a better idea to send the errors please share it :D

"org.json.JSONException: Unterminated string at character" while parsing String to JSONArray

While passing one special use case of String to JSONArray, getting the below error as:
org.json.JSONException: Unterminated string at 25 [character 26 line 1]
My code is as below:
public Object parseResponse(String msg) {
JSONArray taskVariables = null;
try {
if (!StringUtils.isEmpty(msg)) {
taskVariables = new JSONArray(msg);
} else {
taskVariables = createJSONError("Blank or null JSON received.");
}
} catch (JSONException e) {
}
return taskVariables;
}
The input String to the above function is as below:
"[{\"Name\":\"test\\r\\\"}]"
It is parsing till the word "test\r" and the raising the exception while parsing \" which is at the end of the string.
What is the solution for this?

How can I detect if a user enters a string which does not follow my ANTLR grammar rules?

I am making a Computer Algebra System which will take an algebraic expression and simplify or differentiate it.
As you can see by the following code the user input is taken, but if it is a string which does not conform to my grammar rules the error,
line 1:6 mismatched input '' expecting {'(', INT, VAR}, occurs and the program continues running.
How would I catch the error and stop the program from running? Thank you in advance for any help.
Controller class:
public static void main(String[] args) throws IOException {
String userInput = "x*x*x+";
getAST(userInput);
}
public static AST getAST(String userInput) {
ParseTree tree = null;
ExpressionLexer lexer = null;
ANTLRInputStream input = new ANTLRInputStream(userInput);
try {
lexer = new ExpressionLexer(input);
}catch(Exception e) {
System.out.println("Incorrect grammar");
}
System.out.println("Lexer created");
CommonTokenStream tokens = new CommonTokenStream(lexer);
System.out.println("Tokens created");
ExpressionParser parser = new ExpressionParser(tokens);
System.out.println("Tokens parsed");
tree = parser.expr();
System.out.println("Tree created");
System.out.println(tree.toStringTree(parser)); // print LISP-style tree
Trees.inspect(tree, parser);
ParseTreeWalker walker = new ParseTreeWalker();
ExpressionListener listener = new buildAST();
walker.walk(listener, tree);
listener.printAST();
listener.extractExpression();
return new AST();
}
}
My Grammar:
grammar Expression;
#header {
package exprs;
}
#members {
// This method makes the parser stop running if it encounters
// invalid input and throw a RuntimeException.
public void reportErrorsAsExceptions() {
//removeErrorListeners();
addErrorListener(new ExceptionThrowingErrorListener());
}
private static class ExceptionThrowingErrorListener extends BaseErrorListener {
#Override
public void syntaxError(Recognizer<?, ?> recognizer,
Object offendingSymbol, int line, int charPositionInLine,
String msg, RecognitionException e) {
throw new RuntimeException(msg);
}
}
}
#rulecatch {
// ANTLR does not generate its normal rule try/catch
catch(RecognitionException e) {
throw e;
}
}
expr : left=expr op=('*'|'/'|'^') right=expr
| left=expr op=('+'|'-') right=expr
| '(' expr ')'
| atom
;
atom : INT|VAR;
INT : ('0'..'9')+ ;
VAR : ('a' .. 'z') | ('A' .. 'Z') | '_';
WS : [ \t\r\n]+ -> skip ;

A typical parse run with ANTLR4 consists of 2 stages:
A "quick'n dirty" run with SLL prediction mode that bails out on the first found syntax error.
A normal run using the LL prediction mode which tries to recover from parser errors. This second step only needs to be executed if there was an error in the first step.
The first step is kinda loose parse run which doesn't resolve certain ambiquities and hence can report an error which doesn't really exist (when resolved in LL mode). But the first step is faster and delivers so a quicker result for syntactically correct input. This (JS) code shows the setup:
this.parser.removeErrorListeners();
this.parser.addErrorListener(this.errorListener);
this.parser.errorHandler = new BailErrorStrategy();
this.parser.interpreter.setPredictionMode(PredictionMode.SLL);
try {
this.tree = this.parser.grammarSpec();
} catch (e) {
if (e instanceof ParseCancellationException) {
this.tokenStream.seek(0);
this.parser.reset();
this.parser.errorHandler = new DefaultErrorStrategy();
this.parser.interpreter.setPredictionMode(PredictionMode.LL);
this.tree = this.parser.grammarSpec();
} else {
throw e;
}
}
In order to avoid any resolve attempt for syntax errors in the first step you also have to set the BailErrorStrategy. This strategy simply throws a ParseCancellationException in case of a syntax error (similar like you do in your code). You could add your own handling in the catch clause to ask the user for correct input and respin the parse step.

Using Jackcess to retrieve numeric values stored in a text field gives ClassCastException

I am working with Jackcess to read and categorize an access database. It's simply meant to open the database, loop through each line, and print out individual row data to the console which meet certain conditions. It works fine, except for when I try to read numeric values. My code is below. (This code is built into a Swing GUI and gets executed when a jbutton is pressed.)
if (inv == null) { // Check to see if inventory file has been set. If not, then set it to the default reference path.
inv = rPath;
}
if (inventoryFile.exists()) { // Check to see if the reference path exists.
List<String> testTypes = jList1.getSelectedValuesList();
List<String> evalTypes = jList3.getSelectedValuesList();
List<String> grainTypes = jList2.getSelectedValuesList();
StringBuilder sb = new StringBuilder();
for (int i=0; i<=evalTypes.size()-1; i++) {
if (i<evalTypes.size()-1) {
sb.append(evalTypes.get(i)).append(" ");
}
else {
sb.append(evalTypes.get(i));
}
}
String evalType = sb.toString();
try (Database db = DatabaseBuilder.open(new File(inv));) {
Table sampleList = db.getTable("NTEP SAMPLES LIST");
Cursor cursor = CursorBuilder.createCursor(sampleList);
for (int i=0; i<=testTypes.size()-1; i++) {
if ("Sample Volume".equals(testTypes.get(i))) {
if (grainTypes.size() == 1 && "HRW".equals(grainTypes.get(0))) {
switch (evalType) {
case "GMM":
for (Row row : sampleList){
if (null != row.getString("CURRENTGAC")) {}
if ("HRW".equals(row.get("GRAIN")) && row.getDouble("CURRENTGAC")>=12.00) {
System.out.print(row.get("GRAIN") + "\t");
System.out.println(row.get("CURRENTGAC"));
}
}
break;
case "NIRT":
// some conditional code
break;
case "TW":
// some more code
break;
}
}
else {
JOptionPane.showMessageDialog(null, "Only HRW samples can be used for the selected test(s).", "Error", JOptionPane.ERROR_MESSAGE);
}
break;
}
}
}
catch (IOException ex) {
Logger.getLogger(SampleFilterGUI.class.getName()).log(Level.SEVERE, null, ex);
}
When the code is run I get the following error:
java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Double
The following condition looks to be what is throwing the error.
row.getDouble("CURRENTGAC")>=12.00
It appears that when the data is read from the database, the program is reading everything as a string, even though some fields are numeric. I was attempting to cast this field as a double, but java doesn't seem to like that. I have tried using the Double.parseDouble() and Double.valueOf() commands to try converting the value (as mentioned here) but without success.
My question is, how can I convert these fields to numeric values? Is trying to type cast the way to go, or is there a different method I'm not aware of? You will also notice in the code that I created a cursor, but am not using it. The original plan was to use it for navigating through the database, but I found some example code from the jackcess webpage and decided to use that instead. Not sure if that was the right move or not, but it seemed like a simpler solution. Any help is much appreciated. Thanks.
EDIT:
To ensure the program was reading a string value from my database, I input the following code
row.get("CURRENTGAC").getClass().getName()
The output was java.lang.String, so this confirms that it is a string. As was suggested, I changed the following code
case "GMM":
for (Row row : sampleList){
if (null != row.get("CURRENTGAC"))
//System.out.println(row.get("CURRENTGAC").getClass().getName());
System.out.println(String.format("|%s|", row.getString("CURRENTGAC")));
/*if ("HRW".equals(row.get("GRAIN")) && row.getDouble("CURRENTGAC")>=12.00 && row.getDouble("CURRENTGAC")<=14.00) {
System.out.print(row.get("GRAIN") + "\t");
System.out.println(row.get("CURRENTGAC"));
}*/
}
break;
The ouput to the console from these changes is below
|9.85|
|11.76|
|9.57|
|12.98|
|10.43|
|13.08|
|10.53|
|11.46|
...
This output, although looks numeric, is still of the string type. So when I tried to run it with my conditional statement (which is commented out in the updated sample code) I still get the same java.lang.ClassCastException error that I was getting before.

Jackcess does not return all values as strings. It will retrieve the fields (columns) of a table as the appropriate Java type for that Access field type. For example, with a test table named "Table1" ...
ID DoubleField TextField
-- ----------- ---------
1 1.23 4.56
... the following Java code ...
Table t = db.getTable("Table1");
for (Row r : t) {
Object o;
Double d;
String fieldName;
fieldName = "DoubleField";
o = r.get(fieldName);
System.out.println(String.format(
"%s comes back as: %s",
fieldName,
o.getClass().getName()));
System.out.println(String.format(
"Value: %f",
o));
System.out.println();
fieldName = "TextField";
o = r.get(fieldName);
System.out.println(String.format(
"%s comes back as: %s",
fieldName,
o.getClass().getName()));
System.out.println(String.format(
"Value: %s",
o));
try {
d = r.getDouble(fieldName);
} catch (Exception x) {
System.out.println(String.format(
"r.getDouble(\"%s\") failed - %s: %s",
fieldName,
x.getClass().getName(),
x.getMessage()));
}
try {
d = Double.parseDouble(r.getString(fieldName));
System.out.println(String.format(
"Double.parseDouble(r.getString(\"%s\")) succeeded. Value: %f",
fieldName,
d));
} catch (Exception x) {
System.out.println(String.format(
"Double.parseDouble(r.getString(\"%s\")) failed: %s",
fieldName,
x.getClass().getName()));
}
System.out.println();
}
... produces:
DoubleField comes back as: java.lang.Double
Value: 1.230000
TextField comes back as: java.lang.String
Value: 4.56
r.getDouble("TextField") failed - java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Double
Double.parseDouble(r.getString("TextField")) succeeded. Value: 4.560000
If you are unable to get Double.parseDouble() to parse the string values from your database then either
they contain "funny characters" that are not apparent from the samples you posted, or
you're doing it wrong.
Additional information re: your sample file
Jackcess is returning CURRENTGAC as String because it is a Text field in the table:
The following Java code ...
Table t = db.getTable("NTEP SAMPLES LIST");
int countNotNull = 0;
int countAtLeast12 = 0;
for (Row r : t) {
String s = r.getString("CURRENTGAC");
if (s != null) {
countNotNull++;
Double d = Double.parseDouble(s);
if (d >= 12.00) {
countAtLeast12++;
}
}
}
System.out.println(String.format(
"Scan complete. Found %d non-null CURRENTGAC values, %d of which were >= 12.00.",
countNotNull,
countAtLeast12));
... produces ...
Scan complete. Found 100 non-null CURRENTGAC values, 62 of which were >= 12.00.

Iterating over tokens in HIDDEN channel

I am currently working on creating an IDE for the custom, very lua-like scripting language MobTalkerScript (MTS), which provides me with an ANTLR4 lexer. Since the specifications from the language file for MTS puts comments into the HIDDEN_CHANNEL channel, I need to tell the lexer to actually read from the HIDDEN_CHANNEL channel. This is how I tried to do that.
Mts3Lexer lexer = new Mts3Lexer(new ANTLRInputStream("<replace this with the input>"));
lexer.setTokenFactory(new CommonTokenFactory(false));
lexer.setChannel(Token.HIDDEN_CHANNEL);
Token token = lexer.emit();
int type = token.getType();
do {
switch(type) {
case Mts3Lexer.LINE_COMMENT:
case Mts3Lexer.COMMENT:
System.out.println("token "+token.getText()+" is a comment");
default:
System.out.println("token "+token.getText()+" is not a comment");
}
} while((token = lexer.nextToken()) != null && (type = token.getType()) != Token.EOF);
Now, if I use this code on the following input, nothing but token ... is not a comment gets printed to the console.
function foo()
-- this should be a single-line comment
something = "blah"
--[[ this should
be a multi-line
comment ]]--
end
The tokens containing the comments never show up, though. So I searched for the source of this problem and found the following method in the ANTLR4 Lexer class:
/** Return a token from this source; i.e., match a token on the char
* stream.
*/
#Override
public Token nextToken() {
if (_input == null) {
throw new IllegalStateException("nextToken requires a non-null input stream.");
}
// Mark start location in char stream so unbuffered streams are
// guaranteed at least have text of current token
int tokenStartMarker = _input.mark();
try{
outer:
while (true) {
if (_hitEOF) {
emitEOF();
return _token;
}
_token = null;
_channel = Token.DEFAULT_CHANNEL;
_tokenStartCharIndex = _input.index();
_tokenStartCharPositionInLine = getInterpreter().getCharPositionInLine();
_tokenStartLine = getInterpreter().getLine();
_text = null;
do {
_type = Token.INVALID_TYPE;
// System.out.println("nextToken line "+tokenStartLine+" at "+((char)input.LA(1))+
// " in mode "+mode+
// " at index "+input.index());
int ttype;
try {
ttype = getInterpreter().match(_input, _mode);
}
catch (LexerNoViableAltException e) {
notifyListeners(e); // report error
recover(e);
ttype = SKIP;
}
if ( _input.LA(1)==IntStream.EOF ) {
_hitEOF = true;
}
if ( _type == Token.INVALID_TYPE ) _type = ttype;
if ( _type ==SKIP ) {
continue outer;
}
} while ( _type ==MORE );
if ( _token == null ) emit();
return _token;
}
}
finally {
// make sure we release marker after match or
// unbuffered char stream will keep buffering
_input.release(tokenStartMarker);
}
}
The line that caught my eye was the following.
_channel = Token.DEFAULT_CHANNEL;
I don't know much about ANTLR, but apparently this line keeps the lexer in the DEFAULT_CHANNEL channel.
Is the way I tried to read from the HIDDEN_CHANNEL channel right or can't I use nextToken() with the hidden channel?

I found out why the lexer didn't give me any tokens containing the comments - I seem to have missed that the grammar file skips comments instead of putting them into the hidden channel. Contacted the author, changed the grammar file and now it works.
Note to myself: pay more attention to what you read.

For Go (golang) this snippet works for me:
import (
"github.com/antlr/antlr4/runtime/Go/antlr"
)
type antlrparser interface {
GetParser() antlr.Parser
}
func fullText(prc antlr.ParserRuleContext) string {
p := prc.(antlrparser).GetParser()
ts := p.GetTokenStream()
tx := ts.GetTextFromTokens(prc.GetStart(), prc.GetStop())
return tx
}
just pass your ctx.GetSomething() into fullText. Of course, as shown above, whitespace has to go to the hidden channel in the *.g4 file:
WS: [ \t\r\n] -> channel(HIDDEN);