使用面向字节的流（例如FileInputStream / FileOutputStream）从文件读取int值/向文件写入int值是否会访问缓冲区/磁盘4次？

Question

Sample Code is :-

import java.io.*;

public class WriteInt{
    public static void main(String [] args)
    {
    WriteInt obj = new WriteInt();
    obj.write();
    }

    public void write(){
    File file = null;
    FileOutputStream out = null;
    int [] arr = {6};
    try{
    file= new File("CheckSize.txt");
    out = new FileOutputStream(file);
    for(int i =0; i<arr.length;i++)
    {
        System.out.println("Trying to write to file:-"+ file);
        out.write(arr[i]);
    }

    }
    catch(IOException ioex){
    ioex.printStackTrace();
    } 
    finally{
    if(out != null)
    {
        System.out.println("Closing the stream");
        try{
        out.close();
        }   
        catch(IOException ioex){
        ioex.printStackTrace();
        }
    }

    else{
        System.out.println("Stream not open");
        }   
    }
    }

    }

Since I am using Byte-Oriented Stream to write data to a file; My Question is that will the data be written to file in 4 steps (1 byte) in each step. Considering int to be of 4 bytes. Please correct me if I am wrong.

Answer 1

out.write(arr[i]) will write only the lowest byte of int. The best solution is to use java.io.DataOutputStream which has writeInt(int) method.

    DataOutputStream out = new DataOutputStream(new FileOutputStream("file"));
    out.writeInt(arr[i]);

Answer 2

In your example you are using OutputStream.write(int) which writes only byte representation of provided number - only one byte is writen, take a look to OutputStream API . So your file will contain only one byte with 6. If you will try to write a number that is more than 255 - you can expect an exception.

Basically OutputStream requires its subclasses to implement only write(int) method, so other OutputStream methods sends theirs bytes to write(int). However all write methods in FileOutputStream are overridden and utilizes buffered native call that probably tries to send all data at a time.