IO流标-准输出流PrintWriter 和 InputStream字节输入流 ， 字符高级流OutputStreamWriter 和 InputStreamReade

1. 标准输入流

1）InputStream字节输入流 ，源数据源是标准输入设备(键盘、鼠标、触摸屏)等输入设备，InputStream和Reader是所有输入流的抽象基类。

import java.io.IOException;
import java.io.InputStream;

public class Test1 {
    public static void main(String[] args) throws IOException {
        // 输入一句话，然后原样输出

        InputStream in = System.in;

        System.out.println("请输入一句话：");

        byte[] buf = new byte[1024];// 一次读取1024个字节
        int len;
        // buf中包含回车和换行
        len = in.read(buf);
        String str = new String(buf, 0, len);

        System.out.println("你输入的是：" + str);

    }

}

2）根据上一篇文章：IO流  的那首诗。从控制台输入这首诗，然后把这首诗写入文件里。

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;

public class Test2 {
    public static void main(String[] args) throws IOException, UnsupportedEncodingException {

        InputStream in = System.in;
        InputStreamReader reader = new InputStreamReader(in, "GBK");
        BufferedReader br = new BufferedReader(reader);

        File file = new File("D:" + File.separator + "javatest" + File.separator + "f.txt");

        FileWriter writer = new FileWriter(file);
        BufferedWriter beWriter = new BufferedWriter(writer);
        String endString = "bye";// 定义一个输入这首诗结束时的标志；
        System.out.println("请输入一首诗：");
        while (true) {
            String line = br.readLine();
            if (line.equals(endString)) {
                break;
            }
            
            beWriter.write(line);//输入一行
            beWriter.newLine();//换行和回车
        }
        
        beWriter.flush();//刷新缓冲区
        //关闭通道
        beWriter.close();
        writer.close();
    
    }
}

2. 标准输出流(PrintStream)

1）读取以上目录文件，显示到标准输出设备；

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintStream;

public class Test1 {
    public static void main(String[] args) throws FileNotFoundException, IOException {
        
        File file = new File("D:"+File.separator+"javatest"+File.separator+"f.txt");
        //创建管道
        FileReader fReader = new FileReader(file);
        BufferedReader bReader = new BufferedReader(fReader);
        
        PrintStream pStream = System.out;
        
        String line;//定义一个字符串类型
        
        while ((line = bReader.readLine()) != null) {//循环读取文件中每一行，直到为空，就结束。
            pStream.println(line);
        }
        //关闭通道
        bReader.close();
        fReader.close();
    }

}

 3.字符打印流 PrinWriter

用PrintWriter类对象的write()、print()、append()方法实现写入字符到文件，看看结果是否相同？

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;


public class Test1 {
    public static void main(String[] args) throws FileNotFoundException, IOException {
        File file = new File("D:"+File.separator+"javatest"+File.separator+"g.txt");
        
        PrintWriter pWriter = new PrintWriter(file);
        
        pWriter.append("Hello");
        pWriter.write("这个");
        pWriter.println("你好");
        
        pWriter.close();
        
        //将PrintlWriter字符打印流 写文件的信息，输出到控制 台
        InputStream iStream = new FileInputStream("D:"+File.separator+"javatest"+File.separator+"g.txt");
        InputStreamReader iStreamReader = new InputStreamReader(iStream);
        BufferedReader bReader = new BufferedReader(iStreamReader);
        
        String line;
        /*line = bReader.readLine();*/ //写到while循环里
        while ((line = bReader.readLine()) != null) {
            
            System.out.println(line);
            //line = bReader.readLine();
        }
        
        bReader.close();
        iStream.close();
        iStreamReader.close();
    }

}

输出

Hello这个你好

返回结果是相同的，PrinWriter的更多用法，可通过查询JDK API文档

4.Scanner（一般不用，了解即可）

 通过Scanner扫描文件、字节流等等。

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class Test1 {
    public static void main(String[] args) throws FileNotFoundException {
        //通过Scanner扫描文件、字节流等
        File file = new File("d:"+File.separator+"javatest"+File.separator+"c.txt");
        
        Scanner sc = new Scanner(file);
        
        String line;
        while (sc.hasNextLine()) {
            line = sc.nextLine();
            System.out.println(line);
        }
        
        sc.close();
    }
}

 或者通过扫描指定编码文件

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class Test1 {
    public static void main(String[] args) throws FileNotFoundException {
        //通过Scanner扫描文件、字节流等
        /*File file = new File("d:"+File.separator+"javatest"+File.separator+"c.txt");
        
        Scanner sc = new Scanner(file);*/
        Scanner sc = new Scanner(new FileInputStream(new File("d:"+File.separator+"javatest"+File.separator+"c.txt")));
        String line;
        while (sc.hasNextLine()) {
            line = sc.nextLine();
            System.out.println(line);
        }
        
        sc.close();
    }
}