三种java 去掉字符串中的重复字符函数

public static void main(string[] args) {        system.out.println(removerepeatedchar("ddddccffgd"));    }    public static string removerepeatedchar(string s) {        if (s == null)            return s;        stringbuilder sb = new stringbuilder();        int i = 0, len = s.length();        while (i < len) {            char c = s.charat(i);            sb.append(c);            i++;            while (i < len && s.charat(i) == c) {                i++;            }        }        return sb.tostring();    }

//实例二java去掉重复字符串

private static string removesamestring(string str)   {    set
     
       mlinkedset = new linkedhashset
      
       ();    string[] strarray = str.split(" ");    stringbuffer sb = new stringbuffer(); for (int i = 0; i < strarray.length; i++)    {     if (!mlinkedset.contains(strarray[i]))     {      mlinkedset.add(strarray[i]);      sb.append(strarray[i] + " ");     }    }    system.out.println(mlinkedset);    return sb.tostring().substring(0, sb.tostring().length() - 1);     }