IO流

节点流和处理流：#

节点流类型

案例：

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package cn.test;
 
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
 
import org.junit.Test;
 
public class Demo4  {
     
    @Test
    //测试字节输入流
    public void FileInputStreamTest() throws Exception{
        //创建字节输入流
        FileInputStream fs = new FileInputStream("./src/cn/test/Demo4.java");
        //创建一个1024的数节字组，每次从流中最多截取1024字节
        byte[] bytes = new byte[1024];
        //用于保存实际读取的字节数
        int hasRead = 0;
        //使用循环重复的读取流中的字节，直到hasRead=-1
        while ((hasRead = fs.read(bytes))  > 0){
            System.out.println(new String(bytes,0,hasRead));
        }
        fs.close();
    }
     
    @Test
    //测试字符输入流
    public void FileReaderTest() throws IOException{
        //创建字符流
        try {
            FileReader fr = new FileReader("./src/cn/test/Demo4.java");
            //设置每次从文件中读取的文件字符数
            char[] cbuf = new char[256];
            //用于保存实际读取得字符数
            int hasRead = 0;
            while ((hasRead=fr.read(cbuf))>0){
                //将字符串数组转换成字符串输入
                System.out.println(new String(cbuf,0,hasRead));
            }
            fr.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
         
    }
     
    @Test
    //测试字节输出流，读取A文件的流到B文件中
    public void fileOutputStreamTest() throws IOException{
         
        try {
            //创建字节输入流
            FileInputStream fis = new FileInputStream("./src/cn/test/Demo4.java");
            //创建字节输出流，将Demo4.java的内容写到newfile.txt中
            FileOutputStream fos = new FileOutputStream("D:/temp/newfile.txt");
            //创建取字节流的容器字节数组
            byte[] bytes = new byte[1024];
            //用于保存实际读取的字节数
            int hasRead = 0;
            //循环从输入流中读取数据
            while ((hasRead = fis.read(bytes))>0){
                //没读取一次就写入输出流中
                fos.write(bytes, 0, hasRead);
            }
            fis.close();
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
     
    @Test
    //测试字符输出流
    public void fileWriterTest(){
        try {
            FileWriter fw = new FileWriter("D://temp//test.txt");
            //在test.txt中写入内容
            fw.write("hello world!!!\r\n");
            fw.append("China");
            fw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
     
    @Test
    //测试PrintStream字节输出处理流
    public void printStreamTest(){
        try {
            //创建一个输出流
            FileOutputStream fos = new FileOutputStream("D:/temp/test.txt");
            PrintStream ps = new PrintStream(fos);
            //使用PrintStream执行输出，将"普通字符串"写入到test.txt中
            ps.println("普通字符串");
            ps.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
     
    @Test
    //测试转换流和缓冲流
    public void inputStreamReaderTest() throws IOException{
        try {
            //创建字节输入流
            FileInputStream fis = new FileInputStream("D:/temp/test.txt");
            //将字节输入流转换成字符输入流
            InputStreamReader reader = new InputStreamReader(fis);
            //将普通的Reader包装成BufferedReader
            BufferedReader br = new BufferedReader(reader);
            String line = null;
            //采取循环逐行读取
            while ((line = br.readLine()) != null){
                if (line.equals("exit")){
                    System.exit(1);
                }
                System.out.println(line);
            }
            br.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}