Java中定义常量(Constant)

客官°小女子只卖身不卖艺 2022-05-08 13:03 606阅读 0赞

/**
     * Method One
     */
    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 
     */
    enum ConstantEnum {
    	SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
    }
    /**
     * Method Three
     */
    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
     * 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()));
    	}
    }

1.使用Interface

2.使用枚举类型

3.使用static final