java获得实例对象的几种方法

// 1.new 
Dog d1 = new Dog(); 
d1.say(); 
// 2.Class.forName 
Dog d2 = (Dog) Class.forName("com.test.Dog").newInstance(); 
d2.say(); 
// 3.ClassLoader 
ClassLoader c = ClassLoader.getSystemClassLoader(); 
Class classT = c.loadClass("com.test.Dog"); 
Dog d = (Dog) classT.newInstance(); 
d.say(); 
// 4.Constructor

Constructor constructor1 = String.class.getConstructor(StringBuffer.class);
String str2 = (String)constructor1.newInstance(/*"abc"*/new StringBuffer("abc"));
System.out.println(str2.charAt(2));