java 下划线开头_java-清洁代码-以下划线开头的受保护方法的...

我正在阅读Bob叔叔的Clean Code.本书在第16章中介绍了如何重构示例.有一部分我无法抓住以这种方式写作的目的.

>在这里使用保护关键字的目的是什么？

>为什么诸如_getMinimumYear()之类的某些方法以下划线开头？

>为什么要使用一对具有相同名称的方法,而不要使用诸如public abstract int getMinimumYear()的抽象方法？

public abstract class DayDateFactory {

private static DayDateFactory factory = new SpreadsheetDateFactory();

public static void setInstance(DayDateFactory factory) {

DayDateFactory.factory = factory;

}

protected abstract DayDate _makeDate(int ordinal);

protected abstract DayDate _makeDate(int day, Month month, int year);

protected abstract DayDate _makeDate(int day, int month, int year);

protected abstract DayDate _makeDate(java.util.Date date);

protected abstract int _getMinimumYear();

protected abstract int _getMaximumYear();

public static DayDate makeDate(int ordinal) {

return factory._makeDate(ordinal);

}

public static DayDate makeDate(int day, Month month, int year) {

return factory._makeDate(day, month, year);

}

public static DayDate makeDate(int day, int month, int year) {

return factory._makeDate(day, month, year);

}

public static DayDate makeDate(java.util.Date date) {

return factory._makeDate(date);

}

public static int getMinimumYear() {

return factory._getMinimumYear();

}

public static int getMaximumYear() {

return factory._getMaximumYear();

}

}

public class SpreadsheetDateFactory extends DayDateFactory {

public DayDate _makeDate(int ordinal) {

return new SpreadsheetDate(ordinal);

}

public DayDate _makeDate(int day, Month month, int year) {

return new SpreadsheetDate(day, month, year);

}

public DayDate _makeDate(int day, int month, int year) {

return new SpreadsheetDate(day, month, year);

}

public DayDate _makeDate(Date date) {

final GregorianCalendar calendar = new GregorianCalendar();

calendar.setTime(date);

return new SpreadsheetDate(

calendar.get(Calendar.DATE),

Month.fromInt(calendar.get(Calendar.MONTH) + 1),

calendar.get(Calendar.YEAR));

}

protected int _getMinimumYear() {

return SpreadsheetDate.MINIMUM_YEAR_SUPPORTED;

}

protected int _getMaximumYear() {

return SpreadsheetDate.MAXIMUM_YEAR_SUPPORTED;

}

}