java java.lang.enum_java.lang.Enum类方法
Example5.java
public class Example5
{
enum Jobs { ENGINEER,PROGRAMMER,SALES};
enum NewDepartment {ENGINEER, MARKETING, SALES,
HR};
public static void main(String[] args)
{
//compareTo
int i =
NewDepartment.MARKETING.compareTo(NewDepartment.SALES);
int i2 =
NewDepartment.MARKETING.compareTo(NewDepartment.ENGINEER);
int i3 =
NewDepartment.MARKETING.compareTo(NewDepartment.MARKETING);
System.out.printf("NewDepartment.MARKETING
compare to NewDepartment.SALES is %d\n", i);
System.out.printf("NewDepartment.MARKETING
compare to NewDepartment.ENGINEER is %d\n", i2);
System.out.printf("NewDepartment.MARKETING
compare to NewDepartment.MARKETING is %d\n", i3);
//equals
boolean b =
NewDepartment.HR.equals(NewDepartment.SALES);
boolean b2 =
NewDepartment.HR.equals(NewDepartment.HR);
System.out.printf("HR and
NewDepartment.SALES are equal? %b\n", b);
System.out.printf("HR and HR
are equal? %b\n", b2);
//getDeclaringClass
Class c =
NewDepartment.ENGINEER.getDeclaringClass();
Class c2 =
Jobs.ENGINEER.getDeclaringClass();
System.out.printf("NewDepartment.ENGINEER\'s
declaring class is %s\n", c.getName());
System.out.printf("ENGINEER\'s
declaring is %s\n", c2.getName());
//name
String s =
NewDepartment.ENGINEER.name();
String s2 =
NewDepartment.ENGINEER.toString();
System.out.printf("s and s2 are
equals? %b\n", s.equals(s2));
//ordinal
int j =
NewDepartment.ENGINEER.ordinal();
int j2 =
NewDepartment.HR.ordinal();
System.out.printf("NewDepartment.ENGINEER\'s
ordinal is %d\n", j);
System.out.printf("NewDepartment.HR\'s
ordinal is %d\n", j2);
//valueOf
NewDepartment dept =
NewDepartment.valueOf("HR");
boolean b3 =
dept.equals(NewDepartment.HR);
System.out.printf("dept(%s) is
HR? %b\n", dept.name(), b3);
//values
NewDepartment[] depts =
NewDepartment.values();
System.out.printf("NewDepartment
type has %d values, there are %s, %s, %s and %s.\n",
depts.length,
depts[0].name(), depts[1].name(), depts[2].name(),
depts[3].name());
}
}
执行结果如下所示：
NewDepartment.MARKETING compare to NewDepartment.SALES is
-1
NewDepartment.MARKETING compare to NewDepartment.ENGINEER is
1
NewDepartment.MARKETING compare to NewDepartment.MARKETING is
0
HR and NewDepartment.SALES are equal? false
HR and HR are equal? true
NewDepartment.ENGINEER's declaring class is
Example5$NewDepartment
ENGINEER's declaring is Example5$Jobs
s and s2 are equals? true
NewDepartment.ENGINEER's ordinal is 0
NewDepartment.HR's ordinal is 3
dept(HR) is HR? true
NewDepartment type has 4 values, there are ENGINEER, MARKETING,
SALES and HR.
下面介绍上面程序中所涉及的方法：
compareTo：比较两个枚举类型值的顺序。
equals：比较两个枚举类型值是否相等。
getDeclaringClass：取得该枚举类型的声明类。此方法跟Object.getClass()这个方法有点类似，但两者可能得到的结果不同，因为枚举类型类跟一般的类不太一样，它是属于常量且不能实例化，所以使用Object.getClass()方法，在概念上是比较奇怪。
name：取得该枚举类型值的名称字符串。这个方法跟toString有点类似，在没有修改的情况下，两者的返回值是一样的。习惯上的分法是，name方法返回声明时所对应的字符串；toString方法可以美化一下所要返回的字符串，让它看起来更friendly，不过你必须改写toString方法才行。
ordinal：取得该枚举类型的次序。这个号码由0开始编号，以程序7来说ENGINEERING为0、MARKETING为1、SALES为2，而HR为3。
toString：将枚举类型的值，以字符串的类型表示。你可根据程序的需要，自行改写默认的toString方法，让返回的字符串更具信息性。
valueOf：这个方法恰好跟name相反，你可以输入一个字符串，它会返回给你对应到的枚举类型的值。例如NewDepartment.valueOf("HR")会返回NewDepartment.HR。若你所传入的字符串在该枚举类型中，无法找到相对应的值，则会丢出java.lang.IllegalArgumentException异常。这里所传入的字符串是区分大小写的，所以当初在声明枚举类型的值时，也要注意到大小写的问题。
values：取出此枚举类型全部的值。