There are two lines:

1. An instance of the class 'ANTLRInputStream' is created as 'input';
2. An instance of another LabLexer class is created as 'lexer', where the 'input' object from the previous line is passed in the constructor; The 'lexer' constructor specifies that the input argument type is CharStream, but CharStream is an interface. This interface implements the 'ANTLRStringStream' class. The latter has a successor - 'ANTLReaderStream', and it has 'ANTLRInputStream' from the first line. Problem Description: "LabLexer(org.antlr.v4.runtime.CharStream)" in "LabLexer" cannot be applied to "(org.antlr.runtime.ANTLRInputStream)" Unfortunately, I can't change the code, since it's a rather complicated tool for me - the code is written "according to the instructions." Help please!

I tried to change the type of variable - not successful. And add new constructor or change existing - not successful too (variable of CharStream type is initialized in begin of code).

CodePudding user response：

The ANTLRInputStream class is an ANTLR v3 class. You need the v4 variant(s). Do something like this instead:

CharStream charStream = args.length > 0
    ? CharStreams.fromFileName(args[0])
    : CharStreams.fromStream(System.in);

LabLexer lexer = new LabLexer(charStream);
LabParser parser = new LabParser(new CommonTokenStream(lexer));

CodePudding user response：

It's funny, but I quickly found a solution The type of the variable must be the name of the interface. Char input = new ANTLRInputStream(arg); instead of ANTLRInputStream input = new ANTLRInputStream(arg); Sorry for the stupid question, but I'm new to Java))