java IO流

/*输出流必须执行flush(),不然写不进去*/
import java.io.*;
public class TestIO {
    public static void main(String[] args) throws Exception {
      /*单个字符的读取： int read();一个字符被拆成2个8字节，每个8字节占有int的低8位，
      作为一个整数返回。*/
        Reader r1 = new FileReader("C:/Users/well/Desktop/IO测试.txt");
        int b = 0;
        while((b = r1.read())!=-1) {
            System.out.print((char)b);
        }
        System.out.println();
        /*读取的字符暂存到字符数组中，返回本次读取字符的长度*/
      Reader r2 = new FileReader("C:/Users/well/Desktop/IO测试.txt");
        char[] ch = new char[5];
        int len;
        while((len = r2.read(ch))!=-1) {
            System.out.println(new String(ch,0,len));
        }
        /*写入一个字符串*/
        Writer w1 = new FileWriter("C:/Users/well/Desktop/新建.txt");
        w1.write("hello java");
        w1.flush();
        /*字符数组写入*/    /*true,不覆盖文档原来的内容*/
        Writer w2 = new FileWriter("C:/Users/well/Desktop/新建.txt",true);
        String str = new String("      aha 算法");
        char[] ch2 = str.toCharArray();//字符串转换成字符数组
        w2.write(ch2);
        w2.flush();
        /*单个字符写入*/
        Writer w3 = new FileWriter("C:/Users/well/Desktop/新建.txt",true);
        int k = 65;
        w3.write(k);
        w3.flush();
    }
}

 缓冲流

/*输出流必须执行flush(),不然写不进去*/
import java.io.*;
public class TestIO {
    public static void main(String[] args) throws Exception {
        /*buffered类不仅提供缓冲机制，额外提供两种针对字符的读写方法
          （1）按行读取   String readLine();
          （2）写入时随时插入换行 newLine();
          */
      BufferedReader br = new BufferedReader(new FileReader("C:/Users/well/Desktop/IO测试.txt"));
        String str = null;
        while((str = br.readLine())!=null)
            System.out.println(str);
            
        BufferedWriter bw = new BufferedWriter(new FileWriter("C:/Users/well/Desktop/新建.txt"));
        bw.write("Jack Alibaba hangzhou");
        bw.newLine();
        bw.write("Pony tengxun shenzhen");
        bw.newLine();
        bw.write("BaoLuo baidu beijing");
        bw.newLine();
        bw.flush();
    }
}

 数据流

 InputStream和OutputStream

import java.io.*;
public class TestIO {
    public static void main(String[] args) throws Exception {
        InputStream is = new FileInputStream("C:/Users/well/Desktop/IO测试.txt");
        int a;
        while((a = is.read())!=-1)
        System.out.print((char)a);
        
      InputStream is1 = new FileInputStream("C:/Users/well/Desktop/IO测试.txt");
        byte[] bt = new byte[500];
        int b;
        while((b = is1.read(bt))!=-1) {
            System.out.print(new String(bt,0,b)); 
        }
        
        OutputStream os = new FileOutputStream("C:/Users/well/Desktop/IO测试.txt",true);
        os.write(65);
        os.flush();
        byte by = (byte)0x40;
        os.write(by);
        os.flush();
    }
}