A DESCRIPTION OF THE PROBLEM :
Files.writeString is specified to throw IOException when a character cannot be encoded. Instead it uses replacement char "?" when used with sun.nio.cs.ArrayEncoder like Charset.forName("windows-1252"):
probably an error in sun.nio.cs.SingleByte.Encoder.encode(char)

=> Illegal content written on western Windows Systems


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
UnmappableCharacterException
ACTUAL -
JDK uses replacement character

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import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Path;

public class EncodingBug {
public static void main(String[] args) throws IOException {
test("\u00f6\u00fc\u20ac"); // OK, chars of windows-1252
// fails:
test("\u041e");
test("\u0080");
test("\u0080\u041e");
}

private static void test(String s) throws IOException {
Path file = Files.createTempFile("prefix", "suffix");
Charset charset = Charset.forName("windows-1252");
// Charset charset = StandardCharsets.ISO_8859_1; -> UnmappableCharacterException
Files.writeString(file, s, charset); // should throw IOException (UnmappableCharacterException)!!
String s2 = Files.readString(file, charset);
if (!s.equals(s2))
throw new IllegalStateException(s2); // JDK used replacement character :-(
}
}

---------- END SOURCE ----------

FREQUENCY : always