学习java第23天

1.InputStream类

read()方法，逐字地以二进制的原始方法读取数据

public int read(); //读入一个字节，-1表示无

public int read(bytr b[]); //返回读入的字节数

2.OutputStream类

write()方法，是将字节写入流中

public void write (int b); //将参数b的低位字节写入到输出流

public void write (byte b[]); //将字节数组b中的全部字节顺序写入到输出流

Output的另外两个写法是flush()和close()

public void flush(); //刷新缓存，写入到文件

public void close(); //关闭流

3.Reader 类和Writer类

Reader类：输入流，读取的是字符（char）

Writer类：输出流，写入的是字符

public int read(); //将int类转换成char

public int read(char b[]);

public void write(int b); //将参数b的低两字节写入到输出流

public void write(char b[]); //将字符数组b的全部字节顺序写入到输出流

public void write(String s); //将字符串写入流中

4.标准输入和标准输出

System.in 为 InputStream类型

System.out 为 PrintStream类型

System.err 为 PrintStream类型

二进制流的读写：

import java.io.*;

public class Dump {
    public static void main(String[]args) {
        try
        {
            dump( new FileInputStream("aaa.bmp"),
                  new FileOutputStream("bbb.bmp"));
        }
        catch(FileNotFoundException fex)
        {
            fex.printStackTrace();
        }
        catch (IOException ioe)
        {
            ioe.printStackTrace();
        }
    }

    public static void dump(InputStream src, OutputStream dest)
    throws IOException
    {
        InputStream input = new BufferedInputStream(src);
        OutputStream output = new BufferedOutputStream(dest);
        byte[] data = new byte[1024];
        int length = -1;
        while ((length = input.read(data)) != -1) {
            output.write(data, 0, length);
        }
        input.close();
        output.close();
    }
}

字符的读写：

import java.io.*;
public class CopyFileAddLineNumber {
public static void main (String[] args) {
  String infname = "CopyFileAddLineNumber.java";
  String outfname = "CopyFileAddLineNumber.txt";
  if( args.length >= 1 ) infname = args[0];
  if( args.length >= 2 ) outfname = args[1];

  try {
   File fin = new File(infname);
   File fout = new File(outfname);

BufferedReader in = new BufferedReader(new FileReader(fin));
PrintWriter out = new PrintWriter(new FileWriter(fout));

   int cnt = 0; // 行号
   String s = in.readLine();
   while ( s != null ) {
    cnt ++;
    s = deleteComments(s); //去掉以//开始的注释
    out.println(cnt + ": \t" + s ); //写出
    s = in.readLine();    //读入
   }
   in.close();    // 关闭缓冲读入流及文件读入流的连接.
   out.close();
  } catch (FileNotFoundException e1) {
   System.err.println("File not found!" );
  } catch (IOException e2) {
   e2.printStackTrace();
  }
}

static String deleteComments( String s ) //去掉以//开始的注释
{
  if( s==null ) return s;
  int pos = s.indexOf( "//" );
  if( pos<0 ) return s;
  return s.substring( 0, pos );
}
}

对象的读写：

import java.io.*;

class Person implements Serializable
{
String name;
int age;
Person(String name, int age){
  this.name=name; this.age=age;
}
public String toString(){
  return name + "(" + age + ")";
}
};
public class SerializeDemo {
public static void main (String[] args) throws IOException{
  Person [] ps = { new Person("Li",18), new Person("Wang",19) };
  ObjectOutputStream output = new ObjectOutputStream( new FileOutputStream("s.temp") );
  for(Person p : ps) output.writeObject(p);
  output.close();

  ObjectInputStream input = new ObjectInputStream( new FileInputStream("s.temp") );
  Person p = null;
  try{
   while( (p=(Person)input.readObject()) != null ){
    System.out.println(p);
   }
  }catch(ClassNotFoundException ex){}
  catch(EOFException eofex){}
  input.close();
}
}

明天学习内容：

文件及目录

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