Java重构示例一

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Java重构示例一
本文通过Java示例代码片段展示了常用重构原则和技巧，供初级开发人员参考。精致的代码能够清楚传达作者的意图，精致的代码是最好的注释，精致的代码非常容易维护和扩展。程序员阅读精致的代码如同大众欣赏优美的散文一样享受。
1   尽量简洁
1.1   重构前

if ( flag == 1 ){
    return true;
}
else{
    return false;
}

1.2   重构后

return flag == 1;

2   使用三位运算符
2.1   重构前

if ( "Male".equals(gender) ) {
    return "Mr.";
}
else{
    return "Mrs.";
}

2.2   重构后

return "Male".equals(gender) ? "Mr." : "Mrs.";

3   使用常量替换硬编码
3.1   重构前

for (int i = 0; i < 12; i++) {
    this.getDays(i);
    //skip...
}

3.2   重构后

int YEAR_MONTHS = 12;
for (int month = 0; month < Month.YEAR_MONTHS; month++) {
    this.getDays(month);
    //skip...
}

4   使用方法替换反复出现的表达式
4.1   重构前

public boolean isStartAfter(Date date) {
    Calendar calendar = BusinessCalendar.getCalendar();
    calendar.setTime(date);
    int hour = calendar.get(Calendar.HOUR_OF_DAY);
    int minute = calendar.get(Calendar.MINUTE);

    return ( (hour<fromHour)
             || ( (hour==fromHour)
                  && (minute<=fromMinute)
                )
           );
}

public boolean includes(Date date) {
    Calendar calendar = BusinessCalendar.getCalendar();
    calendar.setTime(date);
    int hour = calendar.get(Calendar.HOUR_OF_DAY);
    int minute = calendar.get(Calendar.MINUTE);

    return ( ( (fromHour<hour)
               || ( (fromHour==hour)
                   && (fromMinute<=minute)
                 )
             ) &&
             ( (hour<toHour)
               || ( (hour==toHour)
                    && (minute<=toMinute)
                  )
             )
           );
}

4.2   重构后

private boolean tailGreatHead(int headHour, int headMinute, int tailHour,
           int tailMinute, boolean includeEqual) {
    boolean tailGreatHeadHour = (headHour < tailHour);
    boolean tailEqualHeadHour = (headHour == tailHour);
    boolean tailGreatHeadMinute = (headMinute < tailMinute);
    boolean tailEqualHeadMinute = (headMinute == tailMinute);

    boolean tailGreatEqualHeadMinute = tailGreatHeadMinute || includeEqual
               && tailEqualHeadMinute;

    return (tailGreatHeadHour || (tailEqualHeadHour && tailGreatEqualHeadMinute));
}

private boolean tailGreatHead(int headHour, int headMinute, int tailHour,
           int tailMinute) {
    return tailGreatHead(headHour, headMinute, tailHour, tailMinute, false);
}

private boolean tailGreatEqualHead(int headHour, int headMinute,
           int tailHour, int tailMinute) {
    return tailGreatHead(headHour, headMinute, tailHour, tailMinute, true);
}

public boolean isStartAfter(Date date) {
    Calendar calendar = BusinessCalendar.getCalendar();
    calendar.setTime(date);
    int hour = calendar.get(Calendar.HOUR_OF_DAY);
    int minute = calendar.get(Calendar.MINUTE);

    return this.tailGreatEqualHead(hour, minute, fromHour, fromMinute);
}

public boolean includes(Date date) {
    Calendar calendar = BusinessCalendar.getCalendar();
    calendar.setTime(date);
    int hour = calendar.get(Calendar.HOUR_OF_DAY);
    int minute = calendar.get(Calendar.MINUTE);

    return this.tailGreatEqualHead(fromHour, fromMinute, hour, minute) &&
             this.tailGreatEqualHead(hour, minute, toHour, toMinute);
}

5   及早结束非正常逻辑
5.1   重构前

int count = 0;
if(taskList != null && !taskList.isEmpty()){

//skip...

return count;
}
else {
return count;
}

5.2   重构后

int count = 0;
if(taskList == null || taskList.isEmpty()){
return 0;
}

//skip...

return count;