java学习笔记（7）——I/O流

一、File类

File(File parent, String child);

File(Stirng filename);

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//使用相对路径创建文件和目录

package pack02;





import java.io.File;

import java.io.IOException;





public class FileTest {

public static void main(String[] args) throws IOException{

File file = new File("1.txt");

//file.createNewFile();

file.mkdir();

}

}

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/**

 * 使用绝对路径创建文件或目录

 */

package pack02;





import java.io.File;

import java.io.IOException;





public class FileTest {

public static void main(String[] args) throws IOException{

File file = new File("E:\\javaTest\\lesson\\1.txt");

file.createNewFile();

}

}

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separator 用string类型表示分割符

separatorChar 用char类型表示分隔符

------------------------------------------------------------

/**

 * 不依赖系统平台的绝对路径

 */

package pack02;





import java.io.File;

import java.io.IOException;





public class FileTest {

public static void main(String[] args) throws IOException{

//可以直接用separator表示当前根目录

File fDir = new File(File.separator);

//E:\Javalesson\lesson7\1.txt

String strFile = "JavaLesson" + File.separator + "Lesson7"

+File.separator+"1.txt";

File f = new File(fDir, strFile);

f.createNewFile();

}

}

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File f = new File(fDir, strFile);

f.createNewFile();

f.delete()   //删除文件

f.deleteOnExit()  //当程序终止的时候删除文件

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/**

 * 创建临时文件并在程序结束时删除该文件

 * 创建的临时文件在：

 * 我的电脑-->环境变量-->Temp（指定的目录）

 */

package pack02;





import java.io.File;

import java.io.IOException;





public class FileTest {

public static void main(String[] args) throws IOException{

for(int i=0;i<5;i++){

File f = File.createTempFile("winsun","temp");

f.deleteOnExit();

}

// try {

// Thread.sleep(3000);

// } catch (InterruptedException e) {

// e.printStackTrace();

// }

}

}

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list()方法：返回这个目录下的所有文件名和子目录名

import java.io.File;

import java.io.FilenameFilter;

import java.io.IOException;





public class FileTest {

public static void main(String[] args) throws IOException{

String strFile = "E:"+File.separator+"A"+File.separator+"B"+File.separator;

File f = new File(strFile);

String[] names = f.list(new FilenameFilter(){

public boolean accept(File dir, String name) {

//System.out.println(dir);

return name.indexOf(".java") != -1;

}

});

for(String s:names){

System.out.println(s);

}

}

}

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Decorater 装饰设计模式

节点流：从特定的地方读写的流。

过滤流：使用节点流作为输入或输出。

InputStream

abstract int read(); 读一个字节数据， 返回-1表示到了流的末尾

int read(byte[] b);   将数据读入字节数组 ，最后一次返回实际读取的字节数

int read(byte[] b, int off,  int len);  从指定位置读取， 最后一次返回实际读取的字节数

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import java.io.*;

//将字符串写入文件

public class FileTest {

public static void main(String[] args) throws IOException{

FileOutputStream out = new FileOutputStream("1.txt");

out.write("http://www.baidu.com".getBytes());

out.close();

}

}

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import java.io.*;

//将字符串从文件中读出

public class FileTest {

public static void main(String[] args) throws IOException{

FileOutputStream out = new FileOutputStream("1.txt");

out.write("http://www.baidu.com".getBytes());

out.close();

FileInputStream in = new FileInputStream("1.txt");

byte[] b = new byte[1024];

int len = in.read(b);

System.out.println(new String(b,0,len));

in.close();

}

}

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import java.io.*;

//使用缓冲流写入数据到文件

public class FileTest {

public static void main(String[] args) throws IOException{

FileOutputStream out = new FileOutputStream("2.txt");

BufferedOutputStream bufOut = new BufferedOutputStream(out);

bufOut.write("http:www.baidu.com".getBytes());

bufOut.close(); //注意关闭的时候只需要关闭尾端的流

}

}

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import java.io.*;

//使用缓冲流读出文件中数据

public class FileTest {

public static void main(String[] args) throws IOException{

FileOutputStream out = new FileOutputStream("2.txt");

BufferedOutputStream bufOut = new BufferedOutputStream(out);

bufOut.write("http:www.baidu.com".getBytes());

bufOut.close();

FileInputStream in = new FileInputStream("2.txt");

BufferedInputStream bufIn = new BufferedInputStream(in);

byte[] b = new byte[1024];

int len = bufIn.read(b);

System.out.println(new String(b,0,len));

bufIn.close();

}

}

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读取java中基本数据类型的类 DataInputStream()  DataOutputStream();

import java.io.*;

//使用Data过滤流读写

public class FileTest {

public static void main(String[] args) throws IOException{

FileOutputStream out = new FileOutputStream("2.txt");

BufferedOutputStream bufOut = new BufferedOutputStream(out);

DataOutputStream dataOut = new DataOutputStream(bufOut);

byte b = 3;

int i = 13;

char c = 'a';

float f = 12.3f;

dataOut.writeByte(b);

dataOut.writeInt(i);

dataOut.writeChar(c);

dataOut.writeFloat(f);

dataOut.close();

FileInputStream in = new FileInputStream("2.txt");

BufferedInputStream bufIn = new BufferedInputStream(in);

DataInputStream dataIn = new DataInputStream(bufIn);

byte b1 = dataIn.readByte();


int i1 = dataIn.readInt();

char c1 = dataIn.readChar();

float f1 = dataIn.readFloat();

System.out.println(b1);   //注意读和写的顺序必须一样，才能读对

System.out.println(i1);

System.out.println(c1);

System.out.println(f1);

dataIn.close();

}

}

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管道流  PipedInputStream  PipedOutputStream   他们总是成对出现的(注意这不是过滤流)

import java.io.*;

//使用Data过滤流读写

public class FileTest {



public static void main(String[] args) throws IOException{

PipedOutputStream pipOut = new PipedOutputStream();

PipedInputStream pipIn = new PipedInputStream();

pipOut.connect(pipIn);

new Produce(pipOut).start();

new Consumer(pipIn).start();

}



}

class Produce extends Thread{

private PipedOutputStream pipOut;

public Produce(PipedOutputStream pipOut){

this.pipOut = pipOut;

}

public void run(){

try {

pipOut.write("hello wellcome in file".getBytes());

pipOut.close();

} catch (IOException e) {

e.printStackTrace();

}

}

}

class Consumer extends Thread{

private PipedInputStream pipIn;

public Consumer(PipedInputStream pipIn){

this.pipIn = pipIn;

}

public void run(){

byte[] b = new byte[1024];

try {

int len = pipIn.read(b);

System.out.println(new String(b, 0, len));

} catch (IOException e) {

e.printStackTrace();

}

}

}

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上面是字节流，下面是字符流

OutputStreamWriter() 从字节流到字符流转换

InputStreamRead()  从字符流到字节流转换

通常使用Buffered流进行读写

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import java.io.*;

//使用字符流读写数据

public class FileTest {



public static void main(String[] args) throws IOException{

FileOutputStream out = new FileOutputStream("3.txt");

OutputStreamWriter w = new OutputStreamWriter(out);

BufferedWriter bufW = new BufferedWriter(w);

bufW.write("http://www.baidu.com");

bufW.close();



FileInputStream in = new FileInputStream("3.txt");

InputStreamReader r = new InputStreamReader(in);

BufferedReader bufI = new BufferedReader(r);

String str = bufI.readLine();  //可以读一行

System.out.println(str);

bufI.close();

}

}

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import java.io.*;

//从控制台输入并打印到控制台

public class FileTest {



public static void main(String[] args) throws IOException{

InputStreamReader in = new InputStreamReader(System.in);

BufferedReader bufIn = new BufferedReader(in);

String str;

while((str=bufIn.readLine()) != null){

System.out.println(str);

}

bufIn.close();

}

}

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ASCII :美国信息互换标准编码  是用一个字节来表示字符

GB2312:中华人民共和国汉子信息交换用码   一个中文用两个字节表示

GBK  :k是“扩展”   兼容GB2312，繁体，许多符号，不常用汉字编码

ISO-8859-1 :西方国家使用的字符编码，是一种单字节字符集，而英文只使用了小于128的部分

Unicode :通用的字符集,对所有语言的文字进行了统一的编码，每一个字符用两个字节来表示

但是对英文字符（一个字符用两个字节表示，浪费）

UTF-8 :通用字符集，英文用一个字节表示，是一种用适合长度字节表示不同字符。

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import java.io.*;

import java.nio.*;

import java.nio.charset.Charset;

import java.util.*;

//打印java中能够使用的所有的字符编码

public class FileTest {



public static void main(String[] args) throws IOException{

Map m = Charset.availableCharsets();

Set s = m.keySet();

Iterator i = s.iterator();

while(i.hasNext()){

System.out.println(i.next());

}

}

}

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解码和编码

本地码----->其他编码(编码)

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/**

 * 从屏幕上读取虚拟机信息

 */

package pack02;





import java.util.Properties;





public class FileTest {

public static void main(String[] args){

Properties pps = System.getProperties();

pps.list(System.out);

}

}

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/**

 * 改变虚拟机默认字符集，后从控制台读入解码，再编码为字符串输出

 */

package pack02;





import java.io.IOException;

import java.nio.Buffer;

import java.util.Properties;





import com.sun.jndi.url.iiopname.iiopnameURLContextFactory;





public class FileTest {

public static void main(String[] args) throws IOException{

Properties pps = System.getProperties();

pps.put("file.encoding", "ISO-8859-1");

int data;

byte[] b = new byte[1024];

int len = 0;

while((data=System.in.read()) != 'q'){

b[len] = (byte)data;

len ++;

}

String str = new String(b, 0, len);

System.out.println(str);

}

}

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RandomAccessFile类





package pack02;





import java.io.IOException;

import java.io.RandomAccessFile;





class RandomFileTest{

public static void main(String[] args) throws Exception{

Student s1 = new Student(1,"zs",67);

Student s2 = new Student(2,"ls",89);

Student s3 = new Student(3,"wu",98);

RandomAccessFile raf = new RandomAccessFile("Student.txt","rw");

s1.writeStudent(raf);

s2.writeStudent(raf);

s3.writeStudent(raf);

Student s = new Student();

raf.seek(0);  //指向开始

//length()获取文件长度，  getFilePointer()一个指针

for(long i=0;i<raf.length();raf.getFilePointer()){

s.readStudent(raf);

System.out.println(s.name);

System.out.println(s.num);

System.out.println(s.score);

}

raf.close(); //关闭流

}

}

class Student{

int num;

String name;

double score;

public Student(){



}

public Student(int num,String name,double score){

this.num = num;

this.name = name;

this.score = score;

}

public void writeStudent(RandomAccessFile raf)throws IOException{

raf.writeInt(num);

raf.writeUTF(name); 

raf.writeDouble(score);

}

public void readStudent(RandomAccessFile raf) throws IOException{

num = raf.readInt();

name = raf.readUTF();

score = raf.readDouble();

}

}

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对象序列化

将对象转换为字节流保存起来，并在日后还原这个对象，这种机制叫做对象序列

将一个对象保存到永久存储设备上称为持续性。

一个对象要想能够实现序列化，必须实现Serializable接口或Externalizable接口。

1.Serializable是一个空接口(没有方法)

2.Externalizable继承自Serializable接口

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package pack02;





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;





public class ObjectSerialTest {

public static void main(String[] args) throws IOException, ClassNotFoundException{

Employee e1 = new Employee("zhangsan",25,3000.5);

Employee e2 = new Employee("lisi",24,6000.5);

Employee e3 = new Employee("wangwu",45,60660.5);

FileOutputStream fos = new FileOutputStream("employee.txt");

ObjectOutputStream oos = new ObjectOutputStream(fos);

oos.writeObject(e1);

oos.writeObject(e2);

oos.writeObject(e3);


oos.close();

FileInputStream fis = new FileInputStream("employee.txt");

ObjectInputStream ois = new ObjectInputStream(fis);

Employee e;

for(int i=0;i<3;i++){

e =(Employee)ois.readObject();

System.out.println(e.name);

System.out.println(e.salary);

System.out.println(e.age);

}

ois.close();

}

}

class Employee implements Serializable{

String name;

int age;

double salary;

public Employee() {

super();

}

public Employee(String name, int age, double salary) {

super();

this.name = name;

this.age = age;

this.salary = salary;

}





}

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当一个对象被序列化时，只保存对象的非静态成员变量，不能保存任何的成员方法和静态的成员变量。

如果一个对象的成员变量是一个对象，那么这个对象的数据也会被保存。

如果一个可序列化的对象包含对某个不可序列化的对象的引用，那么整个序列化操作将会失败，

并且会抛出一个NotSerializableException.我们可以将这个引用标记为transient,那么对象任然可以序列化。

------------------------------------------------------------------------------

package pack02;





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;





public class ObjectSerialTest {

public static void main(String[] args) throws IOException, ClassNotFoundException{

Employee e1 = new Employee("zhangsan",25,3000.5);

Employee e2 = new Employee("lisi",24,6000.5);

Employee e3 = new Employee("wangwu",45,60660.5);

FileOutputStream fos = new FileOutputStream("employee.txt");

ObjectOutputStream oos = new ObjectOutputStream(fos);

oos.writeObject(e1);

oos.writeObject(e2);

oos.writeObject(e3);


oos.close();

FileInputStream fis = new FileInputStream("employee.txt");

ObjectInputStream ois = new ObjectInputStream(fis);

Employee e;

for(int i=0;i<3;i++){

e =(Employee)ois.readObject();

System.out.println(e.name);

System.out.println(e.salary);

System.out.println(e.age);

System.out.println(e.thread); //可以被序列化

}

ois.close();

}

}

class Employee implements Serializable{

String name;

int age;

double salary;

//Thread thread  = new Thread(); //不可序列化的对象

//加上transient后可以被序列化

//可以序列化的不想被序列化也可以在前面加上transient

transient Thread thread = new Thread();

public Employee() {

super();

}

public Employee(String name, int age, double salary) {

super();

this.name = name;

this.age = age;

this.salary = salary;

}

}

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重写 readObject()和writeObject()方法

//这两个方法是一个特例，声明为private后在外面能被调用

private void  writeObject(java.io.ObjectOutputStream oos) throws IOException{

oos.writeInt(age);

oos.writeUTF(name);

System.out.println("wirte object);

}

private void readObject(java.io.ObjectInputStream ois) throws IOException{

age = ois.readInt();

name = ois.readUTF();

System.out.println("read object");

}