Java Class.forName()抛出ClassNotFoundException
Java程序的一个思路如下:Java Class.forName()抛出ClassNotFoundException,java,Java,Java程序的一个思路如下: package typeinfo; import static util.Print.*; class Candy { static { print("Loading Candy"); } } class Gum { static { print("Loading Gum"); } } class Cookie { static { print("Loading Cookie"); } } public class SweetShop { publi
package typeinfo;
import static util.Print.*;
class Candy {
static { print("Loading Candy"); }
}
class Gum {
static { print("Loading Gum"); }
}
class Cookie {
static { print("Loading Cookie"); }
}
public class SweetShop {
public static void main(String[] args) {
print("inside main");
new Candy();
print("After creating Candy");
try {
Class.forName("Gum");
} catch(ClassNotFoundException e) {
print("Couldn't find Gum");
}
print("After Class.forName(\"Gum\")");
new Cookie();
print("After creating Cookie");
}
}
/* Output:
inside main
Loading Candy
After creating Candy
Loading Gum
After Class.forName("Gum")
Loading Cookie
After creating Cookie
*/
我期望输出如下:
package typeinfo;
import static util.Print.*;
class Candy {
static { print("Loading Candy"); }
}
class Gum {
static { print("Loading Gum"); }
}
class Cookie {
static { print("Loading Cookie"); }
}
public class SweetShop {
public static void main(String[] args) {
print("inside main");
new Candy();
print("After creating Candy");
try {
Class.forName("Gum");
} catch(ClassNotFoundException e) {
print("Couldn't find Gum");
}
print("After Class.forName(\"Gum\")");
new Cookie();
print("After creating Cookie");
}
}
/* Output:
inside main
Loading Candy
After creating Candy
Loading Gum
After Class.forName("Gum")
Loading Cookie
After creating Cookie
*/
但是得到
inside main
Loading Candy
After creating Candy
Couldn't find Gum
After Class.forName("Gum")
Loading Cookie
After creating Cookie
显然,try块正在抛出一个ClassNotFoundException,这是意外的。你知道为什么代码会抛出这个而不是像预期的那样初始化Gum类吗?你的类在包
typeinfo
中,所以它们的完全限定名是typeinfo.Gum
,typeinfo.Candy
和typeinfo.Cookie
。仅接受完全限定名:
参数:
className
-所需类的完全限定名
将代码更改为:
try {
Class.forName("typeinfo.Gum");
} catch(ClassNotFoundException e) {
print("Couldn't find Gum");
}
我喜欢这个,但为了进一步扩展它,有没有一种方法可以在没有fqn的情况下迭代我的程序包来尝试查找它?@Enjoy87:据我所知,不是以可移植的方式。(如果您有一个特定的jar文件或目录,您可以在其中查找,但这是另一回事。)