yi er san si wu liu qi ba jiu 分别对应123456789,对一段只含有这几种字符串的字符串进行转换

已知：yi er san si wu liu qi ba jiu 分别对应123456789，
对一段只含有这几种字符串的字符串进行转换,用java编程解答

// 字符串替换
public static String Replace(String source,String oldString,String newString){
if (source == null) {
return null;
}
StringBuffer output = new StringBuffer();
int lengOfsource = source.length();
int lengOfold = oldString.length();
int posStart;
int pos;
for (posStart = 0;(pos = source.indexOf(oldString, posStart))>=0;posStart=pos+lengOfold){
output.append(source.substring(posStart,pos));
output.append(newString);
}
if (posStart < lengOfsource) {
output.append(source.substring(posStart));
}
return output.toString();
}

s,b