目录
两个隐式方法
当生成一个枚举值类型的对象时，它会直接用有两个隐式的静态方法
- values()
- valueOf(String name)
/**
* Returns an array containing the constants of this enum
* type, in the order they're declared. This method may be
* used to iterate over the constants as follows:
*
* for(E c : E.values())
* System.out.println(c);
*
* @return an array containing the constants of this enum
* type, in the order they're declared
*/
public static E[] values();
/**
* Returns the enum constant of this type with the specified
* name.
* The string must match exactly an identifier used to declare
* an enum constant in this type. (Extraneous whitespace
* characters are not permitted.)
*
* @return the enum constant with the specified name
* @throws IllegalArgumentException if this enum type has no
* constant with the specified name
*/
public static E valueOf(String name);
个人觉得这两个方法很重要，使用的场景也很多
声明及基本用法
public enum Opt {
ON(1),
OFF(2);
private int value;
private Opt(int value) {
this.value = value;
}
public static Opt fromValue(int value) {
if(value == ON.value) {
return ON;
} else {
return OFF;
}
}
}
// use valueOf(String name) and fromValue(int value)
public Opt getOpt () {
int value = 2;
Opt opt = Opt.fromValue(value);
// String name = "OFF";
// opt = Opt.valueOf(name);
// name must match exactly an identifier used to declare an enum constant in this type
// or will throw IllegalArgumentException
// get all Opt's elements
Opt[] opts = Opt.values();
for (Opt item : opts) {
System.out.println(item.value);
}
return opt;
}
与switch配合
public void withSwitch (int value) {
Opt opt = Opt.fromValue(value);
switch (opt) {
// case Opt.ON: this will prompt 'The qualified case label Snake.Action.LEFT must be replaced with the unqualified enum constant LEFT'
case ON:
System.out.println("on");
break;
case OFF:
System.out.println("off");
break;
}
}
