JavaFileInputStream和ObjectInputStream的区别

FileInputStream类从文件系统中的文件中提取输入字节。 FileInputStream 用于读取原始字节流，例如图像数据。要读取字符流，请考虑使用 FileReader。它应该用于读取面向字节的数据，例如读取音频、视频、图像等。 处理 Input 流的类的层次结构如下：

处理输入流的类层次结构

示例 1：

Java

// Java program to demonstrate Use of FileInputStream class
  
// Importing the desired class
import java.io.FileInputStream;
// Importing input output class from java.io package
import java.io.IOException;
  
// Main class
class FileInputStreamGFG {
  
    // Method 1
    // To read from the file
    private void readFile() throws IOException
    {
  
        // Creating an object of FileInputStream
        FileInputStream fileInputStream = null;
  
        // Try block to check for exceptions
        try {
  
            // Now, creating a FileInputStream by
            //  opening a connection to an actual file
            // The file named by the path name name in the
            // file system
  
            // Here customly we have taken
            //  gfg.txt contains fileInputStream
            = new FileInputStream("gfg.txt");
  
            // data - "Java was called
            // Oak at the beginning."
            int i;
  
            // Reads a byte of data from this input stream
            // using read() method
  
            // Till condition holds true
            while ((i = fileInputStream.read()) != -1) {
  
                // Print the stream
                System.out.print((char)i);
            }
        }
  
        // If there is any exception encountered
        // then execute this block
        finally {
  
            // Stream is not there in file
            if (fileInputStream != null) {
  
                // Then close this file input stream and
                // releases any system resources associated
                // with the stream using close() method
                fileInputStream.close();
            }
        }
    }
  
    // Method 2
    // Main driver method
    public static void main(String[] args)
        throws IOException
    {
  
        // Constructor of this class
        FileInputStreamGFG fileInputStreamGfg
            = new FileInputStreamGFG();
  
        // Calling the readFile() method
        // in the main() method
        fileInputStreamGfg.readFile();
    }
}

输出 ：

Java was called Oak at the beginning.

现在关注输出流，即ObjectInputStream用于反序列化之前使用 ObjectOutputStream 编写的原始数据和对象。只有支持Java.io.Externalizable 接口的对象才能从流中读取。 Java ObjectInputStream 类使您能够从 InputStream 读取Java对象，而不仅仅是原始字节。您将 InputStream 包装在 ObjectInputStream 中，以便您可以从中读取对象。当然，读取的字节必须代表一个有效的、序列化的Java对象。否则，读取对象将失败。通常我们将使用 ObjectInputStream 来读取由Java ObjectOutputStream 写入(序列化)的数据对象。

示例 2：

Java

// Java program to demonstrate Use of ObjectInputStream
// class
  
// Importing required input output classes
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;
  
// Before serialization and de-serialization of objects the
// class of the object must implement java.io.Serializable
  
// Class 1
// Helper clas implementing Serializable interface
class Student implements Serializable {
  
    // Private class member variables
    private static final long serialVersionUID
        = -1438960132000208485L;
    private String name;
    private int age;
  
    // Constructor of this class
    public Student(String name, int age)
    {
        // super keyword refers to parent class
        super();
  
        // this keyword refers to current object instance
        this.name = name;
        this.age = age;
    }
  
    // Getters and Setter for class
    public String getName() { return name; }
  
    public void setName(String name) { this.name = name; }
  
    public int getAge() { return age; }
  
    public void setAge(int age) { this.age = age; }
  
    // Override toString method
    @Override public String toString()
    {
        // Simply return the name and age
        return "Student [name=" + name + ", age=" + age
            + "]";
    }
}
  
// Class 2
// Main class
public class ObjectInputStreamDemo {
  
    // Main driver method
    public static void main(String[] args)
        throws FileNotFoundException, IOException,
               ClassNotFoundException
    {
        // Creating an objec of above class
        // in the main() method
        ObjectInputStreamDemo objectInputStreamDemo
            = new ObjectInputStreamDemo();
  
        // Readfile function call
        objectInputStreamDemo.readStudentObject();
    }
  
    // Member method of main class
    private void readStudentObject()
        throws IOException, FileNotFoundException,
               ClassNotFoundException
    {
  
        // Initially null is set to both streams
        // read and write streams
        FileInputStream fileInputStream = null;
        ObjectInputStream objectInputStream = null;
  
        // Try block to check for exceptions
        try {
  
            // Input stream directory
            fileInputStream
                = new FileInputStream("student.txt");
  
            // Input stream object
            objectInputStream
                = new ObjectInputStream(fileInputStream);
  
            // Creating an object of above class to
            // read an object from the ObjectInputStream
            Student student
                = (Student)objectInputStream.readObject();
  
            // Display message when input stream is
            // completely read
            System.out.println(
                "Successfully read student object from the file.");
  
            // Print an display commands
  
            System.out.println(student);
            System.out.println("Name = "
                               + student.getName());
            System.out.println("Age  = "
                               + student.getAge());
        }
  
        // When an exception is encountered execute the
        // block
        finally {
  
            // If there is nothing to be read
            if (objectInputStream != null) {
                // Then close a ObjectInputStream will will
                //  the InputStream instance from which
                // the ObjectInputStream is reading
                // isong the close() method
                objectInputStream.close();
            }
        }
    }
}

输出：

Successfully read student object from the file.
Student [name=John, age=25]
Name = John
Age  = 25

FileInputStream 和 ObjectInputStream 之间的唯一区别是：

FileInputStream	ObjectInputStream
The Java FileInputStream class, in java.io.FileInputStream, makes it possible to read the contents of a file as a stream of bytes, hence FileInputStream can be used for Serialization.	ObjectInputStream in Java can be used to convert InputStream to object. This process of conversion of the input stream to an object is called deserialization.