java 代码
//example 1 
// zoo.java 
abstract class animal { 
animal(){ 
system.out.println("animal constructor"); 
} 
} 
class tiger extends animal { 
tiger(){ 
system.out.println("tig constructor "); 
} 
} 
class dog extends animal { 
dog(){ 
system.out.println("dog constructor "); 
} 
} 
public class zoo { 
private animal am; //example 1.1 
//private dog am; example 1.2 
private tiger tiger; 
zoo(){ 
tiger = new tiger(); 
am = new dog(); 
} 

public static void main(string [] args){ 
system.out.println("new zoo before"); 
zoo z = new zoo(); 
system.out.println("new zoo after "); 
} 
} 

public static class＜?＞ forname(string classname) 
throws classnotfoundexception 
public static class＜?＞ forname(string name, 
boolean initialize, 
classloader loader) 
throws classnotfoundexception 

private static native class forname0(string name, boolean init , classloader loader) 
throws classnotfoundexception; 

forname0(name, true, classloader.getcallerclassloader()); 

forname0(name, initialize, loader); 

java 代码
//example 2.1 
// zoo.java 
abstract class animal { 
static { 
system.out.println("animal static code block "); 
} 
animal(){ 
system.out.println("animal constructor"); 
} 
} 
class tiger extends animal { 
tiger(){ 
system.out.println("tig constructor "); 
} 
} 
class dog extends animal { 
dog(){ 
system.out.println("dog constructor "); 
} 
} 
public class zoo { 

public static void main(string [] args)throws exception { 
system.out.println("new zoo before"); 
zoo z = new zoo(); 
class c = class.forname("dog",false,z.getclass().getclassloader()); 
system.out.println("initilize before "); 
animal dog = (animal)c.newinstance(); 
system.out.println("new zoo after "); 
} 
} 

java 代码
//example 2.2 
//zoo.java 
abstract class animal { 
static { 
system.out.println("animal static code block "); 
} 
animal(){ 
system.out.println("animal constructor"); 
} 
} 
class tiger extends animal { 
tiger(){ 
system.out.println("tig constructor "); 
} 
} 
class dog extends animal { 
dog(){ 
system.out.println("dog constructor "); 
} 
} 
public class zoo { 

public static void main(string [] args)throws exception { 

class c = zoo.class; 
classloader loader = c.getclassloader(); 
system.out.println("loader before"); 
class dog = loader.loadclass("dog"); 
system.out.println("instance before "); 
animal an = (animal)dog.newinstance(); 
 
} 
}