字节流

字节输出流OutputStream

FileOutputStream类
构造方法

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

public class Demo01 {
    public static void main(String[] args) throws IOException {
        method1();
        method2();
    }
    public static void method1() throws IOException{
        //创建字节输出流对象
        //如果该文件有则覆盖，如果没有则创建
        FileOutputStream fos=new FileOutputStream("E:\java\demo.txt");
        byte[] bytes={97,98,99,100};
        fos.write(100);
        fos.write(bytes, 1, 1);//数组存
        fos.write("你好么".getBytes());//直接扔
        //释放资源
        fos.close();
    }
    //续写
    public static void method2() throws IOException{
        FileOutputStream fos=new FileOutputStream("E:\java\b.txt",true);
        fos.write("
你好么".getBytes());
        //释放资源
        fos.close();
    }
}
IO异常的处理
import java.io.FileOutputStream;
import java.io.IOException;

public class Demo02 {
    public static void main(String[] args) {
        //创建字节输出流对象
        FileOutputStream fos=null;
        try{
            fos=new FileOutputStream("E:\java");
            fos.write("你好".getBytes());
        }catch(IOException e){
            e.printStackTrace();
            //抛出运行异常终止程序
            throw new RuntimeException();
        }finally{
            try {
                fos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
字节输入流InputStream
FileInputStream类
构造方法

方法

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

public class Demo03 {
    public static void main(String[] args) throws IOException {
        method1();
        method2();
        method3();
        method4();
        method5();
    }
    public static void method1() throws IOException{
        //明确数据源
        FileInputStream fos=new FileInputStream("E:\java\demo.txt");
        //从文件中读取一个字节
        int len1=fos.read();
        System.out.println((char)len1);
        len1=fos.read();
        System.out.println((char)len1);
        len1=fos.read();
        System.out.println(len1);
        fos.close();
    }
    //从文件读取内容
    public static void method2() throws IOException{
        FileInputStream fos=new FileInputStream("E:\java\demo.txt");
        int len=0;
        while((len=fos.read())!=-1){
            System.out.println((char)len);
        }
        fos.close();
    }
读取数据read(byte[])方法

//数组读取
    public static void method3() throws IOException{
        FileInputStream fos=new FileInputStream("E:\java\demo.txt");
        byte[] bytes=new byte[2];
        int len=fos.read(bytes);
        System.out.println(new String(bytes));
        System.out.println(len);
        len=fos.read(bytes);
        System.out.println(new String(bytes));
        System.out.println(len);
        fos.close();
    }
    public static void method4() throws IOException{
        FileInputStream fos=new FileInputStream("E:\java\demo.txt");
        byte[] bytes=new byte[2];
        int len=0;
        while((len=fos.read(bytes))!=-1){
            System.out.println(new String(bytes,0,len));//不要后边多出来的    解码
        }
    }
复制文件
//文件复制
    public static void method5() throws IOException{
    FileInputStream fis=newFileInputStream("E:\java\demo.txt");
    FileOutputStream fos=newFileOutputStream("E:\java\a.txt");
        int len=0;
        while((len=fis.read())!=-1){
            fos.write(len);
        }
        fis.close();
        fos.close();
    }
}