Name: saC57035 Date: 12/16/96


The java_io.StreamTokenizer.pushBack() method does not report on
errors which may be produced by its call.

For example, it is possible to call pushBack before any nextToken
call without any errors diagnostics. The initial state of
StreamTokenizer public variables will be returned by nextToken call
in that case, which is equivalent to \0 ordinary character.

It is possible to call pushBack many times as well. This conflicts,
however, with traditional understanding of pushBack operation.
User always receives the same token after any number of
pushBack calls.
 
Here is the example:
----Test.java-------------------
import java.io.*;

public class Test {

public static void main( String argv[] ) {
 StreamTokenizer st = new StreamTokenizer
               (new StringBufferInputStream("line1 \' \n line2 \n line3"));
 try {
   st.pushBack(); // once
   st.pushBack(); //again
   st.nextToken();
   System.out.println(st.ttype); // getting 0 as if it were the first byte
                                 // of the stream!
 } catch (Throwable e) {
   System.out.println("Test failed: "+e+" is thrown");
 }
}

}
-------Output--------------------
0
---------------------------------

The current version of JLS provides no ways of reporting errors
by pushBack(). I have filed the bug against specs as well
(see bug 4022252)
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