Java枚举介绍及使用详解

标签：java枚举   enum   枚举   

在实际编程中，往往存在着这样的“数据集”，它们的数值在程序中是稳定的，而且“数据集”中的元素是有限的。

例如星期一到星期日七个数据元素组成了一周的“数据集”，春夏秋冬四个数据元素组成了四季的“数据集”。

在java中如何更好的使用这些“数据集”呢？在jdk1.5之前我们或许会这样写：

static 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();
		public static final Grade E = new Grade();
	}

@Test
	public void test() {
		print(Grade.A);
	}

	private void print(Grade grade) {
		System.out.println(grade.toString());
	}

	//定义一个枚举类，里面每一个枚举值就代表一个对象
	enum Grade{
		A,B,C,D,E;
	}

@Test
	public void test() {
		print(Grade.A);
	}

	private void print(Grade grade) {
		System.out.println(grade.label);
		System.out.println(grade.getLabel());
	}

	enum Grade {
		A("100-91"), B("90-81"), C("80-71"), D("70-60"), E("60-0");
		private String label;

		private Grade(String label) {
			this.label = label;
		}
		
		private String getLabel(){
			return this.label;
		}
		
	}

@Test
	public void test() {
		print(Grade.B);
	}

	private void print(Grade grade) {
		System.out.println(grade.label);
		System.out.println(grade.getLabel());
		System.out.println(grade.getCNLebal());
	}

	enum Grade {
		A("100-91") {
			@Override
			public String getCNLebal() {
				return "优秀";
			}
		},
		B("90-81") {
			@Override
			public String getCNLebal() {
				return "良好";
			}
		},
		C("80-71") {
			@Override
			public String getCNLebal() {
				return "一般";
			}
		},
		D("70-60") {
			@Override
			public String getCNLebal() {
				return "及格";
			}
		},
		E("60-0") {
			@Override
			public String getCNLebal() {
				return "差";
			}
		};
		private String label;

		private Grade(String label) {
			this.label = label;
		}

		private String getLabel() {
			return this.label;
		}

		public abstract String getCNLebal();

	}

@Test
	public void test() {
		print(Grade.B);
//		Grade.values() 得到所有的枚举值 ，返回一个数组
		System.out.println("分数等级个数为:" + Grade.values().length);
		for (Grade grade : Grade.values()) {
			String name = grade.name();
			System.out.println("当枚举值的name为：" + name);
			int ordinal = grade.ordinal();
			System.out.println("当前枚举值的坐标为：" + ordinal);
		}
		//Grade.valueOf("W")   Grade.valueOf(Grade.class, "E") 将当前字符串转换成一个枚举，如果失败则抛出参数非法异常
		Grade grade = Grade.valueOf("C");
		print(grade);
		Grade grade2 = Grade.valueOf(Grade.class, "E");
		print(grade2);
	}

	private void print(Grade grade) {
		System.out.println(grade.label);
		System.out.println(grade.getLabel());
		System.out.println(grade.getCNLebal());
	}

	enum Grade {
		A("100-91") {
			@Override
			public String getCNLebal() {
				return "优秀";
			}
		},
		B("90-81") {
			@Override
			public String getCNLebal() {
				return "良好";
			}
		},
		C("80-71") {
			@Override
			public String getCNLebal() {
				return "一般";
			}
		},
		D("70-60") {
			@Override
			public String getCNLebal() {
				return "及格";
			}
		},
		E("60-0") {
			@Override
			public String getCNLebal() {
				return "差";
			}
		};
		private String label;

		private Grade(String label) {
			this.label = label;
		}

		private String getLabel() {
			return this.label;
		}

		public abstract String getCNLebal();

	}

public enum ServerCode {
    UNKNOWN(-1, "未知错误"),
    SUCCESS(0, "成功"),
    PARSE_ERROR(100,"返回值解析出错!"),
    NET_IO_ERROR(101,"网络通讯出错！");
   
    private int code = 0;
    private String message = "";

    private ServerCode(int errorCode, String message) {
        this.code = errorCode;
        this.message = message;
    }

    public static ServerCode valueOf(int errorCode) {
        for (ServerCode code : values()) {
            if (code.code == errorCode) {
                return code;
            }
        }
        return UNKNOWN;
    }

    public int code() {
        return code;
    }

    @Override
    public String toString() {
        return message;
    }

常用用法说完了，大体总结一下吧：

Java枚举介绍及使用详解

标签：java枚举   enum   枚举   

原文地址：http://blog.csdn.net/u010358168/article/details/46520687