实例化类有四种方式：
1）使用new操作符
2）调用Class对象的newInstance()方法
3）调用clone()方法，对现有实例的拷贝
4）通过ObjectInputStream的readObject()方法反序列化类
1.new操作符
A a1 = new A();
System.out.println("a1: " + a1);
2.Class.forName()的newInstance方法和Constructor对象的newInstance()方法
Class<A> clazz = (Class<A>) Class.forName("com.bjsxt.singleton.A");
Constructor<A> c = clazz.getDeclaredConstructor(null);
A a2 = c.newInstance();
System.out.println("a2: " + a2);
A a3 = (A) Class.forName("com.bjsxt.singleton.A").newInstance();
System.out.println("a3: " + a3);
3.对象的clone方法
A a3 = (A) a1.clone();
System.out.println("a3: " + a3);
4.getObject反序列化
FileOutputStream fos = new FileOutputStream("d:/a.txt");
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(a1);
oos.close();
fos.close();
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("d:/a.txt"));
A a5 = (A) ois.readObject();
ois.close();
System.out.println("a5: " + a5);
类A的具体代码如下：
class A implements java.io.Serializable {
public A clone() {
return this;
}
}
结果如下：
a1: com.bjsxt.singleton.A@1f6226 a2: com.bjsxt.singleton.A@64ea66 a3: com.bjsxt.singleton.A@158f9d3 a4: com.bjsxt.singleton.A@1f6226 a5: com.bjsxt.singleton.A@13f7281