String str="http://forum.csd::::n.net/PointF:orum/Fo:rum/PostTopic.aspx?forumID=3931c03e-b66c-4189-a4f0-210fd9501803";
        StringBuffer sb=new StringBuffer();
        for(int i=0;i<str.length();i++){
            if(str.charAt(i)!=':'&&str.charAt(i)!='/'){
                sb.append(str.charAt(i)+"");
            }
        }
        System.out.println(sb.toString());

------解决方案--------------------
用正则呗:
Java code

    public static void main(String[] args) {
        String s = "http://forum.csd：：：：n.net/PointF：orum/Fo：rum/PostTopic.aspx?forumID=3931c03e-b66c-4189-a4f0-210fd9501803";
        System.out.println(s.replaceAll("[/|\\:|：|\\s+]", ""));
    }