What are the methods of converting java Object to byte and byte to Object?

Object to byte and byte to Object

Today we will realize how to convert from Object to byte and how to convert from byte to Object.

First, define a class student:

package com.byteToObject; 
import java.io.Serializable; 
public class student implements Serializable{
 
    private int sid;
    private String name;
    public int getSid() {
        return sid;
    }
    public void setSid(int sid) {
        this.sid = sid;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    } 
}

Then define the main method of conversion, which mainly uses streams for conversion:

package com.byteToObject; 
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
 
public class Main { 
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        student stu = new student();
        stu.setSid(123);
        stu.setName("wanger");
        
        ByteArrayOutputStream byam = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(byam);
        oos.writeObject(stu);
        byte[] bytes = byam.toByteArray();
        System.out.println(bytes.toString());
        
        ByteArrayInputStream bais = new ByteArrayInputStream(bytes);
        ObjectInputStream ois = new ObjectInputStream(bais);
        
        student s = (student)ois.readObject();
        System.out.println(s.getName());        
    }
}

Conversion ends.

What does the usage of Object... in java mean?

@SuppressWarnings("unchecked")  
    public List<T> findByConditions(String hql,Object... conditions) throws Exception{  
        Session session = getSessionFactory().getCurrentSession();  
        Query query = session.createQuery(hql);  
        for (int i = 0; i < conditions.length; i++) {  
            query.setParameter(i, conditions[i]);  
        }  
        return query.list();  
    }

Object is the base class of all classes. You can check the jdk documentation to learn about this. All classes inherit from Object.

Object...objects (called variable number of formal parameters) This parameter definition is a form of polymorphic expression when the method parameters are uncertain. That is, this method can pass multiple parameters, and the number of parameters is uncertain. In this way, you need to do some processing accordingly in the method body. Because Object is the base class, the parameter form Object...objects is used to allow all objects inherited from Object to be used as parameters. This method should be relatively rarely used in practice.

Object[] obj is a parameter form composed of an Object array. Note that the parameters of this method are fixed and are an Object array. As for the elements stored in this array, they can be objects of all classes that inherit from Object.

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