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

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：/article/3968175.html

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> 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

}
}