5种创建Java对象的方式

在本篇文章中，将介绍5种创建Java对象的方式。

1. 使用new关键字

package com.idea.test;
public class Student {
    
    private String userName;
    private String nickName;

    public Student(String userName, String nickName) {
        this.userName = userName;
        this.nickName = nickName;
    }
public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        
        this.userName = userName;
    }

    public String getNickName() {
        return nickName;
    }

    public void setNickName(String nickName) {
        this.nickName = nickName;
    }

    @Override
    public String toString() {
        return "Student{" +
                "userName='" + userName + '\'' +
                ", nickName='" + nickName + '\'' +
                '}';
    }
}

public class TestNewStudent{
    public static void main(String[] args){
        Student zhangsan = new Student("Zhangsan","张三");
        Student lisi = new Student();
        lisi.setName("Lisi");
        lisi.setNickname("李四")；
    }}

2. 使用Class类的newInstance()方法

​ 首先，我们可以通过Class.forName()方法动态加载目标类，然后再调用newInstance()方法，动态实例化对象。

package com.idea.test;


public class Student {

    private String userName;
    private String nickName;

    public Student(String userName, String nickName) {
        this.userName = userName;
        this.nickName = nickName;
    }

    public Student() {
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {

        this.userName = userName;
    }

    public String getNickName() {
        return nickName;
    }

    public void setNickName(String nickName) {
        this.nickName = nickName;
    }

    @Override
    public String toString() {
        return "Student{" +
                "userName='" + userName + '\'' +
                ", nickName='" + nickName + '\'' +
                '}';
    }
}

    try {
            Class clz=Class.forName("com.idea.test.Student");
            Student student1=(Student)clz.newInstance();
            student1.setUserName("庞翔");
            student1.setNickName("大个");
            System.out.println("Class 的newInstance方法创建对象"+student1);
        } catch (Exception e) {
            e.printStackTrace();
        }

3. 使用Constructor.newInstance()方法

​ 与Class类的newInstance()方法相似，我们还可以使用java.lang.reflect.Constructor类的newInstance()方法来创建新的对象。

package com.idea.test;


public class Student {

    private String userName;
    private String nickName;

    public Student(String userName, String nickName) {
        this.userName = userName;
        this.nickName = nickName;
    }

    public Student() {
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {

        this.userName = userName;
    }

    public String getNickName() {
        return nickName;
    }

    public void setNickName(String nickName) {
        this.nickName = nickName;
    }

    @Override
    public String toString() {
        return "Student{" +
                "userName='" + userName + '\'' +
                ", nickName='" + nickName + '\'' +
                '}';
    }
}

Constructor<Student> constructorStudent;
        try{
            constructorStudent=Student.class.getConstructor();
            Student student2=constructorStudent.newInstance();
            student2.setUserName("傻逼");
            System.out.println("Contructor newInstance()创建对象"+student2);
        }catch (Exception e){
            e.printStackTrace();
        }

4. 使用反序列化

​ 如果要使用反序列化创建对象，则目标类首先要实现Serializable接口。在本次示例中，我们先创建一个Student对象，并将其保存到data.txt文件中，然后在通过反序列化操作，读取data.txt中的数据，并创建新的对象。

package com.idea.test;


import java.io.Serializable;

public class Student implements Serializable {

    private static final long serialVersionUID = 7497761277861642186L;
    private String userName;
    private String nickName;

    public Student(String userName, String nickName) {
        this.userName = userName;
        this.nickName = nickName;
    }

    public Student() {
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {

        this.userName = userName;
    }

    public String getNickName() {
        return nickName;
    }

    public void setNickName(String nickName) {
        this.nickName = nickName;
    }

    @Override
    public String toString() {
        return "Student{" +
                "userName='" + userName + '\'' +
                ", nickName='" + nickName + '\'' +
                '}';
    }
}

String filePath="D:\\data.txt";
         Student stu=new Student("序列化","反序列化");
        FileOutputStream fileOutputStream=null;
        try{
          fileOutputStream=new FileOutputStream(filePath);
            ObjectOutputStream objectOutputStream=new ObjectOutputStream(fileOutputStream);
            objectOutputStream.writeObject(stu);
            objectOutputStream.flush();
            objectOutputStream.close();
            FileInputStream fileInputStream=new FileInputStream(filePath);
            ObjectInputStream objectInputStream=new ObjectInputStream(fileInputStream);
            Student stu1=(Student) objectInputStream.readObject();
            System.out.println("通过反序列化创建对象"+stu1);

        }catch(Exception e){

        }

5. 使用对象克隆创建新的对象

​ clone()方法可以创建现有对象的副本，但在使用clone()方法前，需保证模板类实现了Cloneable接口，Cloneable接口也是一个标记类接口。