Illegal Character when trying to compile java code

The BOM is generated by, say, File.WriteAllText() or StreamWriter when you don't specify an Encoding. The default is to use the UTF8 encoding and generate a BOM. You can tell the java compiler about this with its -encoding command line option.

The path of least resistance is to avoid generating the BOM. Do so by specifying System.Text.Encoding.Default, that will write the file with the characters in the default code page of your operating system and doesn't write a BOM. Use the File.WriteAllText(String, String, Encoding) overload or the StreamWriter(String, Boolean, Encoding) constructor.

Just make sure that the file you create doesn't get compiled by a machine in another corner of the world. It will produce mojibake.

That's a byte order mark, as everyone says.

javac does not understand the BOM, not even when you try something like

javac -encoding UTF8 Test.java

You need to strip the BOM or convert your source file to another encoding. Notepad++ can convert a single files encoding, I'm not aware of a batch utility on the Windows platform for this.

The java compiler will assume the file is in your platform default encoding, so if you use this, you don't have to specify the encoding.

1. If using an IDE, specify the java file encoding (via the properties panel)
2. If NOT using an IDE, use an advanced text-editor (I can recommend Notepad++) and set the encoding to "UTF without BOM", or "ANSI", if that suits you.

In this case do the following Steps 1-7

In Android Studio

1. Menu -> Edit -> Select All
2. Menu -> Edit -> Cut

3. Open new Notepad.exe

In Notepad

4. Menu -> Edit -> Paste
5. Menu -> Edit -> Select All
6. Menu -> Edit -> Copy 

Back In Android Studio

7. Menu -> Edit -> Paste

http://en.wikipedia.org/wiki/Byte_order_mark

The byte order mark (BOM) is a Unicode character used to signal the endianness (byte order) of a text file or stream. Its code point is U+FEFF. BOM use is optional, and, if used, should appear at the start of the text stream. Beyond its specific use as a byte-order indicator, the BOM character may also indicate which of the several Unicode representations the text is encoded in.

The BOM is a funky-looking character that you sometimes find at the start of unicode streams, giving a clue what the encoding is. It's usually handles invisibly by the string-handling stuff in Java, so you must have confused it somehow, but without seeing your code, it's hard to see where.

You might be able to fix it trivially by manually stripping the BOM from the string before feeding it to javac. It probably qualifies as whitespace, so try calling trim() on the input String, and feeding the output of that to javac.

I had the same problem with a file i generated using the command echo echo "" > Main.java in Windows Powershell. I searched the problem and it seemed to have something to do with encoding. I checked the encoding of the file using file -i Main.java and the result was text/plain; charset=utf-16le.

Later i deleted the file and recreated it using git bash using touch Main.java and with this the file compiled successfully. I checked the file encoding using file -i command and this time the result was Main.java: text/x-c; charset=us-ascii.

Next i searched the internet and found that to create an empty file using Powershell we can use the Cmdlet New-Item. I create the file using New-Item Main.java and checked it's encoding and this time the result was Main.java: text/x-c; charset=us-ascii and this time it compiled successully.