Set集合的toArray()的用法

    Set<Long> supervisionIds = new HashSet<>();
    for(supervisionPlan temp : list){
        supervisionIds.add(temp.getBidSupervisionId());
    }    

　　public String setToarray(Object[] in) {

        StringBuffer str = new StringBuffer();
        for (int i = 0; i < in.length; i++) {
            if (in[i] != null) {
                str .append("‘" + in[i] + "‘,");
            }
        }
        str .insert(0,"(");
        str .deleteCharAt(str.length() - 1);
        str .append(")");

        return str .toString();
    }

　　setToarray(supervisionIds.toArray(new Long[]{}));