Java创建对象的4种方式

使用new关键字

通过new关键字直接在堆内存上创建对象，这样很方便的调用对象的有参和无参的构造函数.

Student stu1 = new Student("lihua");

Class反射调用

使用Java中反射特性，来进行对象的创建。使用

Class

类的

newInstance

方法可以调用无参的构造器来创建对象，如果是有参构造器，则需要使用

Class

的

forName

方法和

Constructor

来进行对象的创建。

Class stuClass = Class.forName("Student");
Constructor constructor = stuClass.getConstructor(String.class);
Student stu2 = (Student) constructor.newInstance("李四");

使用Clone方法

使用Clone的方法：无论何时我们调用一个对象的clone方法，JVM就会创建一个新的对象，将前面的对象的内容全部拷贝进去，用clone方法创建对象并不会调用任何构造函数。要使用clone方法，我们必须先实现Cloneable接口并实现其定义的clone方法。

try
{
Student stu3 = (Student) stu1.clone();
System.out.println(stu3);
}
catch (CloneNotSupportedException e)
{
e.printStackTrace();
}

使用序列化

一个对象实现了

Serializable

接口，就可以把对象写入到文件中，并通过读取文件来创建对象。

String path = Test.class.getClassLoader().getResource("").getPath();
String objectFilePath = path + "out.txt";

ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(objectFilePath));
objectOutputStream.writeObject(stu2);

ObjectInput objectInput = new ObjectInputStream(new FileInputStream(objectFilePath));
Student stu4 = (Student) objectInput.readObject();

示例代码

Student对象，实现

Cloneable

和

Serializable

接口

import java.io.Serializable;

/**
* Created by wzj on 2017/11/3.
*/
public class Student implements Cloneable,Serializable
{
private String name;

public Student(String name)
{
this.name = name;
}

/**
* @return a clone of this instance.
* @throws CloneNotSupportedException if the object's class does not
*                                    support the {@code Cloneable} interface. Subclasses
*                                    that override the {@code clone} method can also
*                                    throw this exception to indicate that an instance cannot
*                                    be cloned.
* @see Cloneable
*/
@Override
protected Object clone() throws CloneNotSupportedException
{
return super.clone();
}
}

测试类

import java.io.*;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;

/**
* Created by wzj on 2017/11/2.
*/
public class Test
{
public static void main(String[] args) throws Exception
{
//1、第一种方式是通过new
Student stu1 = new Student("lihua");System.out.println(stu1);

//2、通过java反射，静态方式
Class stuClass = Class.forName("Student");
Constructor constructor = stuClass.getConstructor(String.class);
Student stu2 = (Student) constructor.newInstance("李四");
System.out.println(stu2);

//3、通过clone实现，必须实现Cloneable接口
try
{
Student stu3 = (Student) stu1.clone();
System.out.println(stu3);
}
catch (CloneNotSupportedException e)
{
e.printStackTrace();
}
//4、通过对象流，必须实现Serializable
String path = Test.class.getClassLoader().getResource("").getPath();
String objectFilePath = path + "out.txt";

ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(objectFilePath));
objectOutputStream.writeObject(stu2);

ObjectInput objectInput = new ObjectInputStream(new FileInputStream(objectFilePath));
Student stu4 = (Student) objectInput.readObject();System.out.println(stu4);
}

}