IO流--字节流

字节流分为：输入流（InputStream）和输出流（outputStream）

（1）字节流读入读出

package com.songyan.bytedemo;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class Demo1 {
public static void main(String[] args) throws IOException {
    testIn2();
}
/**
 * 字节读入1
 * @throws IOException 
 */
public static void testIn() throws IOException
{
    FileInputStream in=new FileInputStream("Demo3.java");
    int by=0;
    while((by=in.read())!=-1)
    {
        System.out.print((char)by);
    }
    in.close();
    
}
/**
 * 字节读入2
 * @throws IOException 
 */
public static void testIn2() throws IOException
{
    FileInputStream in=new FileInputStream("Demo3.java");
    byte[] arr=new byte[8192];
    int len=0;
    while((len=in.read(arr))!=-1)
    {
        System.out.print(new String(arr,0,len));
    }
    in.close();
    
}

/**
 * 字节读入3
 * @throws IOException 
 */
public static void testIn3() throws IOException
{
    FileInputStream in=new FileInputStream("Demo3.java");
    //available()可以获取文件的大小，直接创建一个和文件大小相同的数组
    //但是这种方法只适用于文件大小不太大的情况
    byte[] arr=new byte[in.available()];
    System.out.print(new String(arr));
    in.close();
    
}
/**
 * 字节输出
 * @throws IOException 
 */
public static void testOut() throws IOException
{
    FileOutputStream out=new FileOutputStream("demo1.txt");
    out.write("hahahha".getBytes());
    out.close();
}
}

（2）字节流练习题

package com.songyan.bytedemo;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

/**
 * 拷贝一个图片
 * @author Administrator
 *
 */
public class Test {
public static void main(String[] args) {
    FileInputStream in=null;
    FileOutputStream out=null;
    
    try {
        in=new FileInputStream("E:\\sy\\java\\javaee\\【阶段07】Spring\\spring-day01\\spring-day01\\code\\struts_crm\\WebContent\\images\\info.png");
        out=new FileOutputStream("info.png");
        byte[] arr=new byte[8192];
        int len=0;
        while((len=in.read(arr))!=-1)
        {
            out.write(arr);
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }finally{
        try {
            if(in!=null)
            in.close();
            if(out!=null)
            out.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
}
}