String类的方法-startsWith和 endWith

   String 类中的startsWith和endWith实现的方法基本类似，

    public String getData(String touserId, String desc) {
        JSONObject data = new JSONObject();
        if(touserId.startsWith(Constant.agent_Com_No)){
            data.put("agentid", Constant.agentID);
        }else{
            data.put("agentid", "0");
        }

        ... ... ...
        return data.toJSONString();
    }

public boolean startsWith(String prefix) {
        return startsWith(prefix, 0);
    }

public boolean endsWith(String suffix) {
        return startsWith(suffix, value.length - suffix.value.length);
    }

   public boolean startsWith(String prefix, int toffset) {
        char ta[] = value;
        int to = toffset;
        char pa[] = prefix.value;
        int po = 0;
        int pc = prefix.value.length;
        // Note: toffset might be near -1>>>1.
        if ((toffset < 0) || (toffset > value.length - pc)) {
            return false;
        }
        while (--pc >= 0) {
            if (ta[to++] != pa[po++]) {
                return false;
            }
        }
        return true;
    }