java创建对象的四种方法

Java中创建对象的四种方式

(1) 用new语句创建对象，这是最常见的创建对象的方法。
(2) 运用反射手段,调用java.lang.Class或者java.lang.reflect.Constructor类的newInstance()实例方法。
(3) 调用对象的clone()方法。
(4) 运用反序列化手段，调用java.io.ObjectInputStream对象的 readObject()方法。


一.用new语句创建对象

Java代码

1. User user = new User()

User user = new User()

二.运用反射手段
(1)调用java.lang.Class.newInstance()

Java代码

1. Class.forName(classname).newInstance()
2. Wife wife = (Wife) Class.forName("com.java.clone.Wife").newInstance();

Class.forName(classname).newInstance()Wife wife = (Wife) Class.forName("com.java.clone.Wife").newInstance();

(2)调用java.lang.reflect.Constructor类的newInstance()

Java代码

1. Constructor<Wife> constructor = Wife.class.getDeclaredConstructor(int.class,String.class);
2. Wife wife = (Wife) constructor.newInstance(1,"nihao");

Constructor<Wife> constructor = Wife.class.getDeclaredConstructor(int.class,String.class);Wife wife = (Wife) constructor.newInstance(1,"nihao");

三.调用对象的clone()方法
详情参考：http://ncs123.iteye.com/blog/1775631

Java代码

1. Wife wife = new Wife(1,"wang");
2. Wife wife2 = null;
3. wife2 = (Wife) wife.clone();//运用clone()方法产生新对象

Wife wife = new Wife(1,"wang");Wife wife2 = null;wife2 = (Wife) wife.clone();//运用clone()方法产生新对象

四.运用反序列化手段
被序列化的对象必须implements Serializable

Java代码

1. public class BeanUtil {
3. @SuppressWarnings("unchecked")
4. public static <T> T cloneTo(T src)throws RuntimeException {
5. ByteArrayOutputStream memoryBuffer = new ByteArrayOutputStream();
6. ObjectOutputStream out = null;
7. ObjectInputStream in = null;
8. T dist = null;
10. try {
11. out = new ObjectOutputStream(memoryBuffer);
12. out.writeObject(src);
13. out.flush();
14. in = new ObjectInputStream(new ByteArrayInputStream(
15. memoryBuffer.toByteArray()));
16. dist = (T) in.readObject();
18. } catch (Exception e) {
19. throw new RuntimeException(e);
20. } finally {
21. if (out != null)
22. try {
23. out.close();
24. out = null;
25. } catch (IOException e) {
26. throw new RuntimeException(e);
27. }
28. if (in != null)
29. try {
30. in.close();
31. in = null;
32. } catch (IOException e) {
33. throw new RuntimeException(e);
34. }
35. }
37. return dist;
38. }
40. public static void main(String[] args){
41. Husband husband = new Husband(1);
42. Wife wife = new Wife(1,"jin");
43. husband.setWife(wife);
44. Husband husband2 = cloneTo(husband);//运用反序列生成了一个对象
45. }
46. }