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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 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 Class.forName(classname).newInstance()

  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 Constructor constructor = Wife.class.getDeclaredConstructor(int.class,String.class);

  Wife wife = (Wife) constructor.newInstance(1,"nihao");

  Constructor 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 Wife wife = new Wife(1,"wang");

  Wife wife2 = null;

  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 public class BeanUtil {

  @SuppressWarnings("unchecked")

  public static T cloneTo(T src) throws RuntimeException {

  ByteArrayOutputStream memoryBuffer = new ByteArrayOutputStream();

  ObjectOutputStream out = null;

  ObjectInputStream in = null;

  T dist = null;

  try {

  out = new ObjectOutputStream(memoryBuffer);

  out.writeObject(src);

  out.flush();

  in = new ObjectInputStream(new ByteArrayInputStream(

  memoryBuffer.toByteArray()));

  dist = (T) in.readObject();

  } catch (Exception e) {

  throw new RuntimeException(e);

  } finally {

  if (out != null)

  try {

  out.close();

  out = null;

  } catch (IOException e) {

  throw new RuntimeException(e);

  }

  if (in != null)

  try {

  in.close();

  in = null;

  } catch (IOException e) {

  throw new RuntimeException(e);

  }

  }

  return dist;

  }

  public static void main(String[] args){

  Husband husband = new Husband(1);

  Wife wife = new Wife(1,"jin");

  husband.setWife(wife);

  Husband husband2 = cloneTo(husband);//运用反序列生成了一个对象

  }

  }

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