java 定义 枚举类 enum

	public enum Operation {
		
		Add("Add"),
		
		Upd("Upd"),
		
		Del("Del");
		
		private String value;

		public String getValue() {
			return value;
		}

		private Operation(String value) {
			this.value = value;
		}
		
		public static Operation getInstanceByValue(String type) {
			Operation[] values = Operation.values();
			for (Operation obj : values) {
				if (obj.getValue().equals(type)) {
					return obj;
				}
			}
			return null;
		}
	}