补 I/O基础

1.system.in，system.out示范

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;

import org.junit.Test;
 //文件：1.流式文件(有方向)2.记录式文件(无方向)
 //文件的存取方法：1.顺序存取2.随机存取
 //文件的使用：1.操作接口2.应用程序接口
 //流的定义：有方向的进行流动，文件里面的数据进行操作，传输数据
 //流一般采取缓冲区技术
 //流的作用：传输数据
 //流类： 字符流，字节流...
 //文件类：File文件类，RandomAccessFile随机存取文件类
public class Systeminout {
	@Test
	public void demo1() {
		InputStream in=System.in;
		try {
			for(int i=0;i<10;i++){
			int b=in.read();//阻塞方法，等着输数据
			System.out.println((char)b);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
		//int a=10/0;
	}
     @Test//展示System.out的用法
	public void demo2(){
		 PrintStream out=System.out;
    	 for(int i=0;i<10;i++){
    		 out.println("Hello,World!");
    	 }
	}
     
     
}

2.fileInputStream，fileOutPutStream用法

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import org.junit.Test;

public class FileInOutputStreamDemo {

	@Test
	public void inDemo(){
		try {
			FileInputStream fin = new FileInputStream("d:/a.txt");
			while(fin.available()>0){
				int b = fin.read();
				System.out.print((char)b);
			}
			fin.close();
			//int c = fin.read();//流关闭之后不能再读，否则出异常!!!!!
			//fin.close();//这里没问题。有的流在关闭之后不能再关闭
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	@Test//循环读--法1
	public void inDemo2() throws IOException{
		byte buf[] = new byte[10];
		FileInputStream fin = new FileInputStream("d:/a.txt");
		while(fin.available()>0){
			int len = fin.read(buf);  //总共读了len个字节数据
			for(int i=0;i<len;i++){
				System.out.print((char)buf[i]);
			}
		}
	}
	@Test//循环读--法2
	public void inDemo3() throws IOException{
		byte buf[] = new byte[10];
		FileInputStream fin = new FileInputStream("d:/a.txt");
		int len=0;
		while((len=fin.read(buf))!=-1){
			for(int i=0;i<len;i++){
				System.out.print((char)buf[i]);
			}
		}
	}
	
	@Test//※※※※以后开发时IO异常处理的模板※※※※
	public void inDemo4(){
		byte buf[] = new byte[512];
		FileInputStream fin=null;
		try {
			fin = new FileInputStream("d:/a/a.log");
			int len=0;
			while((len=fin.read(buf))!=-1){
				//下面方式可以处理中文
				String str = new String(buf,0,len,"gbk");
				System.out.print(str);
			}
		}catch (FileNotFoundException e) {
			System.out.println("文件找不到!");
			//e.printStackTrace();
		} catch (IOException e) {
			System.out.println("文件读取失败!");
			//e.printStackTrace();
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			try {
				if(fin!=null){
					fin.close();
				}
			} catch (IOException e) {
				throw new RuntimeException("关流失败!", e);
			}
		}
	}
	
	///////////////////////////////////////////
	@Test
	public void outDemo(){
		try {
			FileOutputStream fout = new FileOutputStream("d:\\a\\dd.txt");//写新文件
			//FileOutputStream fout = new FileOutputStream("d:\\a\\dd.txt",true);//追加方式写
			byte buf[]={48,98,99,32,49,50,51,13,10,65,66};
			fout.write(buf); //输出整个缓冲区的数据
			//fout.write(buf, 0, 11);//输出缓冲区指定范围的数据
			
			fout.close();
			//fout.write(68);//流关闭之后不能再输出，否则出异常
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}
	
}

3.DateInPutStream，DateOutPutStream用法

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

import org.junit.Test;

public class DataInOutputStreamDemo {
	//EOFException : End Of File Exception
	@Test
	public void inDemo() throws IOException{
		
		//文件默认位置为当前项目根目录: 跟src并列位置
		InputStream fin = new FileInputStream("a.txt");
		DataInputStream din = new DataInputStream(fin); //流的套接
		
		/*
		while(din.available()>0){
			int n = din.readInt();
			System.out.println(n);
		}
		*/
		
		for(int i=0;i<100;i++){
			int n = din.readInt();
			System.out.println(n);
		}
		
		double d = din.readDouble();
		System.out.println("d:"+d);
		
		din.close();
	}
	
	@Test
	public void outDemo() throws IOException{
		DataOutputStream dout = new DataOutputStream( new FileOutputStream("a.txt") );
		for(int i=0;i<100;i++){
			dout.writeInt(i);
		}
		
		dout.writeDouble(12.34);
		
		dout.close();
	}
	
	@Test
	public void FibnaciiDemoWriteDemo(){
		try {
			DataOutputStream dout = new DataOutputStream(new FileOutputStream("fib.txt"));
			short i=0,j=1;
			do{
				dout.writeShort(i);
				dout.writeShort(j);
				i=(short) (i+j);
				j=(short) (i+j);
			}while(i>0);//如果符号位变成1，就为负数
			
			dout.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	
	@Test //用available()方法来判断输入结束★★★
	public void FibnaciiDemoReadDemo(){
		try {
			DataInputStream din = new DataInputStream( new FileInputStream("fib.txt") );
			while(din.available()>0){
				short n1 = din.readShort();
				short n2 = din.readShort();
				System.out.print(n1+" "+n2+" ");
			}
			System.out.println();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	@Test //捕获异常控制输入结束★★★  
	public void FibnaciiDemoReadDemo2(){
		try {
			DataInputStream din = new DataInputStream( new FileInputStream("fib.txt") );
			while(true){
				short n1 = din.readShort();
				System.out.print(n1+" ");
				short n2 = din.readShort();
				System.out.print(n2+" ");
			}
		} catch (EOFException e) {
		  System.out.println();
		  System.out.println("Over!");			
		}catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	
}

4.Objectstream用法

import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

import org.junit.Test;

public class ObjectStreamDemo {
	
	@Test
	public void writeDemo(){
		Person p1 = new Person("Jack",22);
		Person p2 = new Person("Tom",12);
		Person p3 = new Person("Rose",23);
		Person p4 = new Person("张三",31);
		Person p5 = new Person("李四",32);
		
		try {
			
			ObjectOutputStream out = new ObjectOutputStream( new FileOutputStream("persons.dat"));
			out.writeObject(p1);  
			out.writeObject(p2);
			out.writeObject(p3);
			out.writeObject(p4);
			out.writeObject(p5);
			out.close();
			
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		
	}
	
	//☆☆☆注意：对象流的读取必须采用捕捉异常的方式控制结束，不能采用available()>0
	@Test
	public void readDemo(){
		ObjectInputStream in=null;
		try {
			in = new ObjectInputStream(new FileInputStream("persons.dat"));
			while(true){
				Person p = (Person) in.readObject();
				System.out.println(p);
			}
			
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (EOFException e) {
			System.err.println("数据加载完毕....");
		}catch (IOException e) {
			e.printStackTrace();
		}catch (Exception e) {
			e.printStackTrace();
		}finally{
			if(in!=null){
				try {
					in.close();
				} catch (IOException e) {
					throw new RuntimeException("关流失败", e);
				}
			}
		}
		
	}
}

//☆☆☆用对象流写的对象必须要实现Serializable接口----贴标签技术
class Person implements Serializable{
	private String name;
	private int age;
	public Person(String name, int age) {
		this.name = name;
		this.age = age;
	}
	public Person() {
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	@Override
	public String toString() {
		return name + ", " + age;
	}
	
}

5.fileCopy

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;

import org.junit.Test;

public class fileCopy1 {
    @Test //拷贝文件: 从一个文件读取数据，写到另一个文件，循环进行“边读边写”
    public void test1() throws IOException{
    	//文本文件
    	FileInputStream fin=new FileInputStream("a.txt");
    	FileOutputStream fout=new FileOutputStream("aa.txt");
    	
    	
    	/*/二进制文件:图像、声音、可执行程序类
		FileInputStream fin = new FileInputStream("d:/a/11.jpg");
		FileOutputStream fout = new FileOutputStream("d:/11.jpg");*/
    	byte buf[]=new byte[128];
    	int len=0;
    	while((len=fin.read(buf))!=-1){
    		fout.write(buf,0,len);
    	}
    	
    	fin.close();
		fout.close();
    }
    
    
    @Test//拷贝文件变种--加密、解密: 从一个文件读取数据，把数据按某种规则改变一下，再写到另一个文件，循环进行“边读边写”
    public void test2() throws IOException{
    	//文本文件
    	FileInputStream fin=new FileInputStream("a.txt");
    	FileOutputStream fout=new FileOutputStream("bb.txt");
    	
    	byte buf[] = new byte[64];
		int len = 0;
		while( (len=fin.read(buf))!=-1){
			//加密或解密
		    for(int i=0;i<len;i++){
		    	buf[i]=(byte) (buf[i]-1);
		    }
		    
		    fout.write(buf, 0, len);
		}
		fin.close();
		fout.close();
    }
    
    @Test//网络其实也是一个IO的终端
    public void test3() throws IOException{
    	URL url=new URL("http://www.hncu.net");
    	URLConnection con=url.openConnection();
    	InputStream in=con.getInputStream();
    	byte buf[] = new byte[512];
		int len=0;
		while((len=in.read(buf))!=-1){
			String str = new String(buf,0,len,"utf-8");
			System.out.print(str);
		}
		in.close();
    }
}