学步园

好处，和传统方法比较

public class Enumeration {
	
	public void test(){
		print(Grade.A);
	}
	//想让下面的函数只能打印A，B，C，D
	public void print(Grade g){
		
	}
		
}

//方法一
/*
class Grade{
	private Grade(){}
	public static final Grade A = new Grade();
	public static final Grade B = new Grade();
	public static final Grade C = new Grade();
	public static final Grade D = new Grade();
	
}
*/
//方法二

enum Grade{
	A,B,C,D;
}

还可对枚举封装对象，改成

enum Grade{   //class  A 100-90  B 89-80 C 79-70 D 69-0
	A("100-90"),B("100-90"),C("100-90"),D("100-90");
	
	private String value;  //封装对应的分数
	private Grade (String value){
		this.value = value;
	}
	
	public String getValue(){
		return this.value;
	}
}

还可以改成带有抽象方法的枚举

//带抽象方法的枚举
enum Grade{   //class  A 100-90  B 89-80 C 79-70 D 69-0
	A("100-90"){
		public String localValue(){
			return "优秀";
		}
	}
	
	,B("100-90"){
		public String localValue(){
			return "良好";
		}
	}
	,C("100-90"){
		public String localValue(){
			return "一般";
		}
	}
	,D("100-90"){
		public String localValue(){
			return "差";
		}
	};
	
	private String value;  //封装对应的分数
	private Grade (String value){
		this.value = value;
	}
	
	public String getValue(){
		return this.value;
	}
	
	public abstract String localValue();
}