java实例化对象的四种方式

article/2025/10/26 0:55:06

java实例化对象的4种方式

用new 语句创建对象，这是最常用的创建对象方法。

package test;public class Father {public void print() {System.out.println("我是father");}
public static void main(String[] args) {Father f = new Father();f.print();}
}

运用反射手段，调用Java.lang.Class或者java.lang.reflect.Constructor类的newInstance()实例方法。

package test;public class Father {public void print() {System.out.println("我是father");}
public static void main(String[] args) {try {Class<?> cla = Class.forName("test.Father");try {Father f = (Father)cla.newInstance();f.print();} catch (InstantiationException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();}} catch (ClassNotFoundException e) {e.printStackTrace();}}
}

3. 调用对象的clone()方法
clone()表示克隆，使用这个实例化一个对象的前提是前面已经有一个实例化过的对象

User user1 = new User(1,"dan");User user2 = null;user2 = (User) user1.clone();

运用反序列化手段，调用java.io.ObjectInputStream对象的readObject()方法。
序列化：将对象状态转化为可保持或传输的格式的过程，被序列化的对象必须implments Serializable
反序列化：将流转化成对象的过程
当两个进程在进行远程通信时，彼此可以发送各种类型的数据。无论是何种类型的数据，都会以二进制序列的形式在网络上传送。发送方需要把这个Java对象转换为字节序列，即java对象序列，才能在网络上传送，即序列化过程；接收方则需要把字节序列再恢复为java对象，即反序列化。

package test;import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;public class Father  {//序列化public static void serial(String fileName) {Test t = new Test("wo");try {ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(fileName));objectOutputStream.writeObject(t);objectOutputStream.close();} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}//反序列化public static void deserialize(String fileName){   try {ObjectInputStream inputStream = new ObjectInputStream(new FileInputStream(fileName));Test t2 = (Test)inputStream.readObject();inputStream.close();t2.test();} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}catch (ClassNotFoundException e) {e.printStackTrace();}}
public static void main(String[] args) {Father.serial("D:\\test.txt");System.out.println("序列化完成");Father.deserialize("D:\\test.txt");System.out.println("反序列化完成");}
}
class Test implements Serializable{public String name;public Test(String name) {this.name = name;}public void test() {System.out.println(name);}
}