在Java中定义常量(Constant) ，简化代码

/**

* Method One，采用接口(Interface)的中变量默认为static final的特性。

*/

interface ConstantInterface
{

String SUNDAY = "SUNDAY";

String MONDAY = "MONDAY";

String TUESDAY = "TUESDAY";

String WEDNESDAY = "WEDNESDAY";

String THURSDAY = "THURSDAY";

String FRIDAY = "FRIDAY";

String SATURDAY = "SATURDAY";

}

/**

* Method Two ，引入的Enum类型。

*/

enum ConstantEnum
{

SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY

}

/**

* Method Three，在普通类中使用static final修饰变量的方法。

*/

class ConstantClassField {

public static final String SUNDAY = "SUNDAY";

public static final String MONDAY = "MONDAY";

public static final String TUESDAY = "TUESDAY";

public static final String WEDNESDAY = "WEDNESDAY";

public static final String THURSDAY = "THURSDAY";

public static final String FRIDAY = "FRIDAY";

public static final String SATURDAY = "SATURDAY";

}

/**

* Method Four，方法四类似方法三，但是通过函数来获取常量。

* http://www.ibm.com/developerworks/cn/java/l-java-interface/index.html
*/

class ConstantClassFunction {

private static final
String SUNDAY = "SUNDAY";

private static final String MONDAY = "MONDAY";

private static final String TUESDAY = "TUESDAY";

private static final String WEDNESDAY = "WEDNESDAY";

private static final String THURSDAY = "THURSDAY";

private static final String FRIDAY = "FRIDAY";

private static final String SATURDAY = "SATURDAY";

public static String getSunday() {

return SUNDAY;

}

public static String getMonday() {

return MONDAY;

}

public static String getTuesday() {

return TUESDAY;

}

public static String getWednesday() {

return WEDNESDAY;

}

public static String getThursday() {

return THURSDAY;

}

public static String getFirday() {

return FRIDAY;

}

public static String getSaturday() {

return SATURDAY;

}

}

public class TestConstant {

static final String day = "saturday";

public static void main(String[] args) {

System.out.println("Is today Saturday?");

System.out.println(day.equalsIgnoreCase(ConstantInterface.SATURDAY));

System.out.println(day.equalsIgnoreCase(ConstantEnum.SATURDAY.name()));

System.out.println(day.equalsIgnoreCase(ConstantClassField.SATURDAY));

System.out.println(day.equalsIgnoreCase(ConstantClassFunction

.getSaturday()));

}

}