java枚举（java枚举）.docVIP

java枚举（java枚举） Talk about using enumerations in Java Programmers moving from C++ to Java always have a lot of complaints about Java at first, with no enumeration as a more prominent problem. So why doesnt Java support enumerations? What does it mean to support enumeration from the point of view of procedural language? Can we find a way to meet the requirements of C++ programmers for enumerations? Well, now lets discuss the problem. Enumeration type (Enumerated, Types) Lets take a look at the following small program: Enum, Day, {SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY}; This statement provides a user friendly method of variable definition that enumerates all possible values of this data type, i.e., Monday through Sunday. Aside from the specific programming language, the core functionality of enumerations should be: The type of security (Type Safety) The compact and effective enumeration definition (Compact, Efficient Declaration numerical of Enumerated Values) The seamless and other parts of the program (Seamless integration with other interaction language features) The operation of the high efficiency (Runtime efficiency) Now lets discuss each of these characteristics one by one. 1. types of security The enumeration declaration creates a new type. It is different from other existing types, including primitive types (integers, floats, etc.) and other enumerated types within the scope of the current scope (Scope). When you assign values to functions, integer types and enumerated types are not interchangeable (unless you do explicit type conversions), the compiler will enforce that. For example, define such a function with an enumeration specified above: Public void foo (Day); If you call this function with integers, the compiler will give you the wrong one. Foo (4); / / compilation error If you follow this standard, then Pascal, Ada, and C++ are strictly supported enumerations, and the C language is not. 2. compact, efficient enumeration numeric