java版本的escape和unescape函数

// java版本的escape和unescape函数

class  EscapeUnescape
{
 public static String  escape (String src)
 {
  int i;
  char j;
  StringBuffer tmp = new StringBuffer();
  tmp.ensureCapacity(src.length()*6);

  for (i=0;i<src.length() ;i++ )
  {

   j = src.charAt(i);

   if (Character.isDigit(j) || Character.isLowerCase(j) || Character.isUpperCase(j))
    tmp.append(j);
   else
    if (j<256)
    {
    tmp.append( "%" );
    if (j<16)
     tmp.append( "0" );
    tmp.append( Integer.toString(j,16) );
    }
    else
    {
    tmp.append( "%u" );
    tmp.append( Integer.toString(j,16) );
    }
  }
  return tmp.toString();
 }

 public static String  unescape (String src)
 {
  StringBuffer tmp = new StringBuffer();
  tmp.ensureCapacity(src.length());
  int  lastPos=0,pos=0;
  char ch;
  while (lastPos<src.length())
  {
   pos = src.indexOf("%",lastPos);
   if (pos == lastPos)
    {
    if (src.charAt(pos+1)=='u')
     {
     ch = (char)Integer.parseInt(src.substring(pos+2,pos+6),16);
     tmp.append(ch);
     lastPos = pos+6;
     }
    else
     {
     ch = (char)Integer.parseInt(src.substring(pos+1,pos+3),16);
     tmp.append(ch);
     lastPos = pos+3;
     }
    }
   else
    {
    if (pos == -1)
     {
     tmp.append(src.substring(lastPos));
     lastPos=src.length();
     }
    else
     {
     tmp.append(src.substring(lastPos,pos));
     lastPos=pos;
     }
    }
  }
  return tmp.toString();
 }

 public static void main(String[] args) 
 {
  String tmp="~!@#$%^&*()_+|\\=-,./?><;'][{}\"";
  System.out.println("testing escape : "+tmp);
  tmp =escape(tmp);
  System.out.println(tmp);
  System.out.println("testing unescape :"+tmp);
  System.out.println(unescape(tmp));
 }
}