enum的使用

public enum SystemType {

    WINDOWS
        {
            
            public String ()
            {
                return "Windows"
            }
        },

    LINUX
        {
            
            public String ()
            {
                return "Linux";
            }
        },

    MAC
        {
            
            public String ()
            {
                return "Mac";
            }
        };

    public String ()
    {
        throw new IllegalStateException("SystemType.getValue() should be overrided");
    }
}

EnumUtils.isValidEnum(SystemType.class, "someString")