[antlr-interest] Error for class ANTLRInputStream

[Borneq]

import org.antlr.runtime.*;

public class v3me {
	public static void main(String[] args) throws Exception {
		ANTLRFileStream fileStream = new ANTLRFileStream("ANTLR.g");
		ANTLRInputStream input = new ANTLRInputStream(System.in);
        }
}

I debug. can step over ANTLRFileStream but on ANTLRInputStream is
exception ClassNotFoundException.
I don;t know why can find one class and can't find second