/** 
 * 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
 * 采用了Java 5.0中引入的Enum类型 (推荐使用)
 */  
enum ConstantEnum {  
	SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY  
} 
 
/** 
 * Method Three 
 * 采用了在普通类中使用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 
 * 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()));  
	}  
}