編碼，應(yīng)按照總-分的思路編寫：先寫整體的大框架，后續(xù)再實現(xiàn)具體細節(jié)。
假設(shè)要實現(xiàn)用戶登錄判斷的需求，其中需要判斷驗證碼、用戶名、密碼等是否合法及用戶名與密碼是否匹配，那么我們第一步的代碼應(yīng)如下：

第一步：編寫整體框架

public class LoginService {

    public String login(UserInfo userInfo) {
        boolean codeIsLegal = verifyCode(userInfo.getCode());
        if (!codeIsLegal) {
            return "驗證碼錯誤！";
        }
        boolean nameIsLegal = verifyName(userInfo.getName());
        if (!nameIsLegal) {
            return "用戶名不合法！";
        }
        boolean passIsLegal = verifyPass(userInfo.getPassword());
        if (!passIsLegal) {
            return "密碼不合法";
        }
        boolean nameMatchedPass = verifyNameNPass(userInfo.getName(), userInfo.getPassword());
        if (!nameMatchedPass) {
            return "用戶名與密碼不匹配！";
        }
        return "登錄成功";
    }

}

class UserInfo {
    private String name;
    private String password;
    private String code;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }
}

第二步：實現(xiàn)具體判斷邏輯

public class LoginService {

    public String login(UserInfo userInfo) {
        boolean codeIsLegal = verifyCode(userInfo.getCode());
        if (!codeIsLegal) {
            return "驗證碼錯誤！";
        }
        boolean nameIsLegal = verifyName(userInfo.getName());
        if (!nameIsLegal) {
            return "用戶名不合法！";
        }
        boolean passIsLegal = verifyPass(userInfo.getPassword());
        if (!passIsLegal) {
            return "密碼不合法";
        }
        boolean nameMatchedPass = verifyNameNPass(userInfo.getName(), userInfo.getPassword());
        if (!nameMatchedPass) {
            return "用戶名與密碼不匹配！";
        }
        return "登錄成功";
    }

    private boolean verifyCode(String code) {
        return code.equals("6666");
    }

    private boolean verifyName(String name) {
        return name.equals("admin");
    }

    private boolean verifyPass(String password) {
        return password.equals("admin");
    }
    
    private boolean verifyNameNPass(String name, String password) {
        return true;
    }
}

class UserInfo {
    private String name;
    private String password;
    private String code;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }
}

醬紫寫，思路清晰代碼層次分明，易于閱讀及維護。
但代碼層次太分明時，也會有弊端。如下所示：模擬請求API接口

public class HttpService {

    public JSONObject queryData(RequestVO vo) {
        Map<String, String> header = buildHeader(vo);
        JSONObject body = buildBody(vo);
        String result = exeHttpRequest(header, body);
        return JSON.parseObject(result);
    }

    private String exeHttpRequest(Map<String, String> header, JSONObject body) {
        return "{\"code\":0,\"msg\":\"請求成功\"}";
    }

    private JSONObject buildBody(RequestVO vo) {
        String sign = generateSign(vo);
        JSONObject body = new JSONObject();
        body.put("name", vo.name);
        body.put("phone", vo.phone);
        body.put("sign", sign);
        return body;
    }

    private Map<String, String> buildHeader(RequestVO vo) {
        String sign = generateSign(vo);
        Map<String, String> header = new HashMap<>(2);
        header.put("content-type", "application/json");
        header.put("sign", sign);
        return header;
    }

    private String generateSign(RequestVO vo) {
        return MD5Encoder.encode((vo.name + vo.phone).getBytes());
    }
}

class RequestVO {
    String name;
    String phone;
}

從代碼中可看出，sign被計算了兩次。但假如為了復(fù)用header中生成的sign，整個代碼就不會這么清晰了。
具體實踐中，應(yīng)根據(jù)實際情況權(quán)衡是否要做到如此層次分明：
當sign的計算較簡單時，可以重復(fù)計算；
當sign的計算較耗費資源時，則應(yīng)復(fù)用。