java输入输出流

1.java输入输出流分类

1.1按数据流的方向不同分为输入流和输出流

注意：输入输出相对于程序来说的,而不是文件

1.2按处理数据单位不同分为字节流和字符流：

字节流按字节处理，字符流按字符（两个字节，unicode编码，较适合中文处理）处理。凡是以Stream结尾的都是字节流，凡是以Reader或是Writer结尾的都是字符流。

                  字节流(Stream)      字符流(两个字节)

输入流            InputStream                Reader

输出流           OutputStream              Writer

1.3按功能不同分为节点流和处理流

节点流可以套上处理流，这样可以套用处理流中的方法，比如BufferedReader有readLine每次读取一行的方法。

转换流：InputStreamReader和OutputStreamWriter用于与字节数据到字符数据之间转换。(a)InputStreamReader需和InputStream“套接”，InputStream转换成Reader. (b)OutputStreamWriter需和OutputStream“套接”，OutputStream转换成Writer.

需要提醒的是PrintStream和printWriter，这两个输出流不会抛出异常，而且有自动flush功能；对于printWriter即可以用writer字符输出流也可以用outputstream字节输出流来初始化。

2.输入输出流基本样例

下面的例子涵盖了基础的FileInputStream/FileOutputStream节点流，BufferedReader理流以及InputStreamReader转换流，DataOutputStream,ObjectOutputStream（需要实现Serializable接口）， PrintStream和PrintWriter

package com.zgd.io;

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.PrintWriter;
import java.io.Serializable;

public class CopyFile {

public static void main(String[] args) throws IOException {
//1.InputStream  Reader Buffered 节点流 处理流
// 转换流 InputStreamReader OutputStreamReader
String DIR="/home/zgd/workspace/IO/src/com/zgd/io/";
//1.FileInputStream
FileInputStream fis = new FileInputStream(DIR+"copyfile.txt");
FileOutputStream fos = new FileOutputStream(DIR+"writefile.txt");

if(fis != null){
int b;
while((b = fis.read()) != -1){
//System.out.println((char)b);
fos.write(b);
}
}

fis.close();
fos.close();

//2.BufferedReader   InputStreamReader转换流
BufferedReader buff = new BufferedReader(new InputStreamReader(new FileInputStream(DIR+"copyfile.txt")));
String temp=null;
while((temp=buff.readLine())!=null){
System.out.println(temp);
}
buff.close();

//3.DataOutputStream
DataOutputStream out1 = new DataOutputStream(new FileOutputStream(DIR+"writefile.txt"));
out1.writeInt(3);
out1.writeDouble(1.445);
out1.writeDouble(323.44);
out1.writeDouble(-23.44);
out1.close();

DataInputStream in1 = new DataInputStream(new FileInputStream(DIR+"writefile.txt"));
int count = in1.readInt();
for(int i=1; i<=count; ++i){
double d = in1.readDouble();
System.out.println(d);
}

//4.ObjectOutputStream

Student s1 = new Student(1,"zenggd",20);
Student s2 = new Student(2,"harry",22);

ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(DIR+"object.dat"));
oos.writeObject(s1);
oos.writeObject(s2);
oos.writeObject(null);//
oos.flush();
oos.close();

ObjectInputStream ois = new ObjectInputStream(new FileInputStream(DIR+"object.dat"));
try {
Student t ;
while((t= (Student) ois.readObject()) != null) {
System.out.println(t);
}

} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

//5.PrintStream PrintWriter
PrintWriter pw = new PrintWriter(new FileOutputStream(DIR+"ps.txt"));
String zgd="zgd is a good boy";
double dd = 3.44223;
pw.println(zgd);
pw.println(dd);
pw.close();

}
}

class Student implements Serializable{
private int num=0;
private String name="";
private int age=0;

public Student(int num, String name, int age) {
super();
this.num = num;
this.name = name;
this.age = age;
}

public int getNum() {
return num;
}
public void setNum(int num) {
this.num = num;
}
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 "Student [num=" + num + ", name=" + name + ", age=" + age + "]";
}

}