Exception in thread "main" java.util.zip.ZipException: Not in GZIP format

Good Moorning,

I'm trying in my program to Compress/Decompress data using GZIP streams and=
 when using the charset "ISO-8859-1", everything working well but when chan=
ging the charset to "UTF-8", i'm getting the Error message "Exception in th=
read "main" java.util.zip.ZipException: Not in GZIP format".
this is my code:

public static String compress(String str) throws IOException {
            if (str == null || str.length() == 0) {
                return str;
            }
            System.out.println("String length : " + str.length());
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            GZIPOutputStream gzip = new GZIPOutputStream(out);
            gzip.write(str.getBytes());
            gzip.close();
            String outStr = out.toString("UTF-8");
            System.out.println("Output String lenght : " + outStr.length());
            System.out.println("Output : " + outStr.toString());
            return outStr;
     }
        
     public static String decompress(String str) throws IOException {
        if (str == null || str.length() == 0) {
           return str;
        }
            System.out.println("Input String length : " + str.length());
            GZIPInputStream gis = new GZIPInputStream(new ByteArrayInputStre=
am(str.getBytes("UTF-8")));
            BufferedReader bf = new BufferedReader(new InputStreamReader(gis=
, "UTF-8"));
            String outStr = "";
            String line;
            while ((line=bf.readLine())!=null) {
              outStr += line;
            }
            System.out.println("Output String lenght : " + outStr.length());
            return outStr;
     }
      
     public static void main(String[] args) throws IOException {

            
            String string = "my data";
            System.out.println("after compress:");
            String compressed = compress(string);
            System.out.println(compressed);
            System.out.println("after decompress:");
            String decomp = decompress(compressed);
            System.out.println(decomp);
     
     }

Please can you people help me find a solutioN??