Nếu nhu cầu là chuyển đổi "òéışöç-> oeisoc", bạn có thể sử dụng điểm này:
public class AsciiUtils {
    private static final String PLAIN_ASCII =
      "AaEeIiOoUu"    // grave
    + "AaEeIiOoUuYy"  // acute
    + "AaEeIiOoUuYy"  // circumflex
    + "AaOoNn"        // tilde
    + "AaEeIiOoUuYy"  // umlaut
    + "Aa"            // ring
    + "Cc"            // cedilla
    + "OoUu"          // double acute
    ;
    private static final String UNICODE =
     "\u00C0\u00E0\u00C8\u00E8\u00CC\u00EC\u00D2\u00F2\u00D9\u00F9"             
    + "\u00C1\u00E1\u00C9\u00E9\u00CD\u00ED\u00D3\u00F3\u00DA\u00FA\u00DD\u00FD" 
    + "\u00C2\u00E2\u00CA\u00EA\u00CE\u00EE\u00D4\u00F4\u00DB\u00FB\u0176\u0177" 
    + "\u00C3\u00E3\u00D5\u00F5\u00D1\u00F1"
    + "\u00C4\u00E4\u00CB\u00EB\u00CF\u00EF\u00D6\u00F6\u00DC\u00FC\u0178\u00FF" 
    + "\u00C5\u00E5"                                                             
    + "\u00C7\u00E7" 
    + "\u0150\u0151\u0170\u0171" 
    ;
    // private constructor, can't be instanciated!
    private AsciiUtils() { }
    // remove accentued from a string and replace with ascii equivalent
    public static String convertNonAscii(String s) {
       if (s == null) return null;
       StringBuilder sb = new StringBuilder();
       int n = s.length();
       for (int i = 0; i < n; i++) {
          char c = s.charAt(i);
          int pos = UNICODE.indexOf(c);
          if (pos > -1){
              sb.append(PLAIN_ASCII.charAt(pos));
          }
          else {
              sb.append(c);
          }
       }
       return sb.toString();
    }
    public static void main(String args[]) {
       String s = 
         "The result : È,É,Ê,Ë,Û,Ù,Ï,Î,À,Â,Ô,è,é,ê,ë,û,ù,ï,î,à,â,ô,ç";
       System.out.println(AsciiUtils.convertNonAscii(s));
       // output : 
       // The result : E,E,E,E,U,U,I,I,A,A,O,e,e,e,e,u,u,i,i,a,a,o,c
    }
}
JDK 1.6 cung cấp lớp java.text.N normalizer có thể được sử dụng cho nhiệm vụ này.
Xem một ví dụ ở đây