io流之节点流inputstream、outputstream、reader、writer

 

例子程序：读取工作空间下

package io;
import java.io.*;
public class TestFileInputStream {
  public static void main(String[] args) {
    int b = 0;
    FileInputStream in = null;
    try {
      in = new FileInputStream("F:\share\workspace\J2SE\src\io\TestFileInputStream.java");
    } catch (FileNotFoundException e) {
      System.out.println("找不到文件"); 
      System.exit(-1);
    }
    try {
      long num = 0;
      while((b=in.read())!=-1){
        System.out.print((char)b); 
        num++;
      }
      in.close();  
      System.out.println();
      System.out.println("共读取了 "+num+" 个字节");
    } catch (IOException e1) {
      System.out.println("文件读取错误"); System.exit(-1);
    }
  }
}

结果：由于read方法一次读取的是一个字节，一个汉字占的2个字节，所以打印出来汉字是乱码，

package io;
import java.io.*;
public class TestFileInputStream {
  public static void main(String[] args) {
    int b = 0;
    FileInputStream in = null;
    try {
      in = new FileInputStream("F:\share\workspace\J2SE\src\io\TestFileInputStream.java");
    } catch (FileNotFoundException e) {
      System.out.println("找不到文件"); 
      System.exit(-1);
    }
    try {
      long num = 0;
      while((b=in.read())!=-1){
        System.out.print((char)b); 
        num++;
      }
      in.close();  
      System.out.println();
      System.out.println("共读取了 "+num+" 个字节");
    } catch (IOException e1) {
      System.out.println("文件读取错误"); System.exit(-1);
    }
  }
}
共读取了 737 个字节

OutputStream:

 

例子程序：文件的复制，如果文件不存在会自动创建HW.java 文件

package io;
import java.io.*;

public class TestFileOutputStream {
  public static void main(String[] args) {
      int b = 0;
      FileInputStream in = null;
      FileOutputStream out = null;
      try {
        in = new FileInputStream("f:/share/j2se/IO/HelloWorld.java");
        out = new FileOutputStream("f:/share/j2se/IO/HW.java");
        while((b=in.read())!=-1){
          out.write(b);
        }
        in.close(); 
        out.close();
      } catch (FileNotFoundException e2) {
        System.out.println("找不到指定文件"); System.exit(-1);
      } catch (IOException e1) {
        System.out.println("文件复制错误"); System.exit(-1);
      }
      System.out.println("文件已复制");
  }
}

 Reader：

例子程序：读取本身

package io;

import java.io.*;
public class TestFileReader {
  public static void main(String[] args) {
    FileReader fr = null; 
    int c = 0;
    try {
      fr = new FileReader("F:\share\workspace\J2SE\src\io\TestFileReader.java");
      int ln = 0;
      while ((c = fr.read()) != -1) {
        //char ch = (char) fr.read();
        System.out.print((char)c);
        //if (++ln >= 100) { System.out.println(); ln = 0;}
      }
      fr.close();
    } catch (FileNotFoundException e) {
      System.out.println("找不到指定文件");
    } catch (IOException e) {
      System.out.println("文件读取错误");
    }

  }
}

Writer：

 例子程序“

package io;

import java.io.*;
public class TestFileWriter {
  public static void main(String[] args) {
    FileWriter fw = null;
    try {
      fw = new FileWriter("f:\share\j2se\IO\unicode.dat");
      //char在计算机是用数字表示的，直接把数字写进文件。char是2个字节，最大是65535
      //这里就是吧Unicode大多数国家的字符都写进了文件
      for(int c=0;c<=50000;c++){
        fw.write(c);
        if(c%100==0){
            fw.write("
");
        }
      }
      fw.close();
    } catch (IOException e1) {
        e1.printStackTrace();
      System.out.println("文件写入错误");
      System.exit(-1);
    }
  }
}

结果：


 
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