IO流（流？）
1.0 概念和分类
2.0 字节输出流
（1）输入一个字节
import java.io.FileOutputStream;
import java.io.IOException;
public class Main{
public static void main(String[] args) throws IOException {
FileOutputStream fos=new FileOutputStream("Demo01\\a.txt");
fos.write(97);
fos.close();
}
}
（2）多个字节的输入
import java.io.FileOutputStream;
import java.io.IOException;
public class Main{
public static void main(String[] args) throws IOException {
FileOutputStream fos=new FileOutputStream("Demo01\\b.txt");
byte bytes[]={65,66,67,68};//ABCD
//第一种
fos.write(bytes);
//第二种
fos.write(bytes,1,3);
//第三种
String s="你好,很高兴认识你";
byte[] bytes1 = s.getBytes();
System.out.println(bytes1);//[B@1c53fd30
fos.write(bytes1);
fos.close();
}
}
字节输出流的续写和换行
import java.io.FileOutputStream;
import java.io.IOException;
public class Main{
public static void main(String[] args) throws IOException {
FileOutputStream fos=new FileOutputStream("Demo01\\c.txt",true);
fos.write("我说很高兴我能遇见你".getBytes());
for (int i = 0; i <5 ; i++) {
fos.write("我也是".getBytes());
fos.write("\r\n".getBytes());
}
fos.close();
}
}
3.字节输入流
单个字符读取
import java.io.FileInputStream;
import java.io.IOException;
public class Main{
public static void main(String[] args) throws IOException {
FileInputStream fis=new FileInputStream("Demo01\\b.txt");
int len=0;
while((len=fis.read())!=-1)
{
System.out.print(len+" ");
}
fis.close();
}
}
打印结果：
97 98 99
多个字符的读取
import java.io.FileInputStream;
import java.io.IOException;
public class Main{
public static void main(String[] args) throws IOException {
FileInputStream fis=new FileInputStream("Demo01\\b.txt");
byte []bytes=new byte[1024];
int len=0;
while((len=fis.read(bytes))!=-1)
{
System.out.println(len);
String s = new String(bytes, 0, len);
System.out.println(s);
}
}
}
打印结果：
8
ABCDEabc
4.字符输入流
import java.io.FileReader;
import java.io.IOException;
public class Main{
public static void main(String[] args) throws IOException {
FileReader fr=new FileReader("Demo01\\b.txt");
int len=0;
/*读取一个字符
while ((len=fr.read())!=-1) {
System.out.print((char)len);
}*/
/*读取多个字符
char chars[]=new char[1024];
while((len=fr.read(chars))!=-1)
{
System.out.println(new String(chars,0,len));
}*/
fr.close();
}
}
5.字符输出流
import java.io.FileWriter;
import java.io.IOException;
public class Main{
public static void main(String[] args) throws IOException {
FileWriter fw=new FileWriter("Demo01\\b.txt");
fw.write(97);
fw.flush();
//fw.close();
}
}
flush()和close()的区别
字节输出流的续写和换行
6.try...catch()处理流中的异常
import java.io.FileWriter;
import java.io.IOException;
public class Main{
public static void main(String[] args) {
FileWriter fs=null;
try{
fs=new FileWriter("Dem01\\b.txt");
for(int i=0;i<5;i++)
{
fs.write("你好"+i+"\r\n");
}
}
catch(IOException e)
{
System.out.println(e);
}
finally {
if(fs!=null)
{
try {
fs.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
JDK 7对其优化
6.属性集
import java.util.Enumeration;
import java.util.Properties;
import java.util.Set;
public class Main{
public static void main(String[] args) {
Properties prop=new Properties();
prop.setProperty("Jin","27");
prop.setProperty("V","25");
prop.setProperty("JK","25");
Set set = prop.stringPropertyNames();
for (String s : set) {
System.out.println(prop.get(s));
}
}
}
store方法
import java.io.FileWriter;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Properties;
import java.util.Set;
public class Main{
public static void main(String[] args) throws IOException {
Properties prop=new Properties();
prop.setProperty("Jin","27");
prop.setProperty("V","25");
prop.setProperty("JK","23");
prop.store(new FileWriter("Demo01\\b.txt"),"practice");
}
}
load方法
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Properties;
import java.util.Set;
public class Main{
public static void main(String[] args) throws IOException {
Properties prop=new Properties();
prop.load(new FileReader("Demo01\\b.txt"));
Set set = prop.stringPropertyNames();
for (String s : set) {
System.out.println(s+"="+prop.getProperty(s));
}
}
}
缓冲流
1.0 字节缓冲输出流
2.字节缓冲输入流
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
public class Main{
public static void main(String[] args) throws IOException {
FileInputStream fis=new FileInputStream("Demo01\\c.txt");
BufferedInputStream input=new BufferedInputStream(fis);
int len=0;
byte []bytes=new byte[1024];
while((len=input.read(bytes))!=-1)
{
System.out.println(new String(bytes,0,len));
}
input.close();
}
}
3.字符缓冲输出流
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
public class Main{
public static void main(String[] args) throws IOException {
BufferedWriter bw=new BufferedWriter(new FileWriter("Demo01\\c.txt"));
for(int i=0;i<5;i++)
{
bw.write("你好，我叫赤木晴子");
bw.newLine();
}
bw.flush();
bw.close();
}
}
打印结果:
4.字符缓冲输入流
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class Main{
public static void main(String[] args) throws IOException {
BufferedReader br=new BufferedReader(new FileReader("Demo01\\c.txt"));
String s;
while((s=br.readLine())!=null)
{
System.out.println(s);
}
br.close();
}
}
转换流
1.0 OutputStreamWrite
2.InputStreamReader
转换流的练习
将GBK文件转化为UTF-8文件
import java.io.*;
public class Main{
public static void main(String[] args) throws IOException {
InputStreamReader isr=new InputStreamReader(new FileInputStream("Demo01\\我是一个GBK文件.txt"),"GBK");
OutputStreamWriter osw=new OutputStreamWriter(new FileOutputStream("Demo01\\转化后的UTF-8文件"),"UTF-8");
int len=0;
while((len=isr.read())!=-1)
{
osw.write(len);
}
isr.close();
osw.close();
}
}
序列化与非序列化
序列化
ObjectOutputStream
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
public class Main{
public static void main(String[] args) throws IOException {
ObjectOutputStream oos=new ObjectOutputStream(new FileOutputStream("Demo01\\a.txt"));
oos.writeObject(new Person("百里玄策",18));
oos.close();
}
}
ObjectInputStream
import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
public class Main{
public static void main(String[] args) throws IOException, ClassNotFoundException {
ObjectInputStream ois=new ObjectInputStream(new FileInputStream("Demo01\\a.txt"));
Object o = ois.readObject();
ois.close();
System.out.println(o);
}
}
transient关键字修饰的成员变量不能被序列化（瞬态关键字）
import java.io.Serializable;
public class Person implements Serializable {
private String name;
private transient int age;
public Person(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
@Override
public String toString() {
return "Person{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
public void setAge(int age) {
this.age = age;
}
public Person() {
}
}
import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
public class Test {
public static void main(String[] args) throws IOException,ClassNotFoundException {
ObjectInputStream ois=new ObjectInputStream(new FileInputStream("Demo01\\a.txt"));
Object o = ois.readObject();
ois.close();
System.out.println(o);
}
}
打印结果：
Person{name='百里玄策', age=0}
打印流
import java.io.FileNotFoundException;
import java.io.PrintStream;
public class Main{
public static void main(String[] args) throws FileNotFoundException {
System.out.println("我在控制台输出");
PrintStream ps=new PrintStream("输出流");
System.setOut(ps);
System.out.println("我在输出流中输出");
}
}