java高级_01
输入流:
从文件输入到内存，即：读文件
输出流：
从内存输出到文件，即：写文件
一 节点流(进行文件读写的基本流)
1 字符流（以字符char为单位进行读写）
1.1 抽象父类
Reader
Writer
1.2 针对文件的字符流
FileReader
read() read(char[])
FileWriter
write() write(char[]) write(String)
2 字节流（以字节byte为单位进行读写）
2.1 抽象父类
InputStream
OutputStream
2.2 针对文件的字节流
FileInputStream
read() read(byte[])
FileOutputStream
write(int) write(byte[])
二 处理流(对节点流的包装，使文件读写更快速更方便)
2.1 缓冲流(效率高)
字符缓冲流
BufferedReader
readLine()
BufferedWriter
newLine()
字节缓冲流
BufferedInputStream
read(byte[],int,int)
BufferedOutputStream
write(byte[],int,int)
2.2 打印流（格式化）
PrintWrite
print(String) println(String)
PrintStream
print(String) println(String)
2.3 Scanner
next() nextInt() nextDouble()
2.4 数据流
DataInputStream
DataOutputStream
2.5 对象流(要操作的对象的类必须实现Serializable接口)
ObjectOutputStream
ObjectInputStream
练习：
1 复制文件
从a.txt复制出b.txt
注意：怎么判断文件读到结尾
2 把歌词一句一句打印出来
3 循环输入用户信息，保存到文件
模拟登陆：键盘输入用户名和密码，检查用户名密码是否正确
import java.io.File;
import java.io.IOException;
public class TestFile {
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
File file = new File("a.txt");
System.out.println("exists=" + file.exists());
file.createNewFile();//创建file对象对应的文件
System.out.println("exists=" + file.exists());
System.out.println("dir=" + file.isDirectory());
System.out.println("file=" + file.isFile());
}
}
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class Testreaderwriter {
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
//1 流对象
FileReader fr = new FileReader("a.txt");
//2 读取字符
char c = (char)fr.read();
System.out.println(c);
//3 关闭
fr.close();
FileWriter fw = new FileWriter("a.txt",true);
//2 写入字符a
fw.write('a');
fw.write("bcdefg");
//3 关闭
fw.close();
}
}
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Arrays;
public class TestFileStream {
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
//读文件，输入流
//1 搭建输入流
//FileInputStream fis1 = new FileInputStream("a.txt");
File file = new File("a.txt");
File file1 = new File("b.txt");
//如果是文件，就进行读写
if(file.isFile())
{
FileInputStream fis2 = new FileInputStream(file);
//2 从流中读取数据
byte b = (byte)fis2.read();
byte b1 = (byte)fis2.read();
byte[] bs = new byte[5];
fis2.read(bs);
System.out.println("b = " + b + " b1 = " + b1);
System.out.println("bs = " + Arrays.toString(bs));
//3 关闭流
fis2.close();
//1 构建文件输出流
FileOutputStream fos2 = new FileOutputStream(file1);
//2 从流中读取数据
fos2.write(55);
fos2.write(56);
fos2.write(bs);
//3 关闭流
fos2.close();
}
}
}
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class TestBuffered {
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
//缓冲流
//1 节点流
FileWriter fw = new FileWriter("c.txt");
//2 处理流包装节点流
BufferedWriter bw = new BufferedWriter(fw);
bw.write("这是第一行");
bw.newLine();
bw.write("这是第二行");
bw.newLine();
bw.close();
//1 节点流
FileReader fr = new FileReader("c.txt");
//2 处理流包装节点流
BufferedReader br = new BufferedReader(fr);
System.out.println(br.readLine());
System.out.println(br.readLine());
br.close();
}
}
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
public class TestObjectStream {
/**
* @param args
*/
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
FileOutputStream fileOutputStream = new FileOutputStream("b.txt");
ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream);
objectOutputStream.writeObject(new User("张三","123456"));
objectOutputStream.close();
FileInputStream fileInputStream = new FileInputStream("b.txt");
ObjectInputStream objectInputStream = new ObjectInputStream(fileInputStream);
User user = (User)objectInputStream.readObject();
System.out.println(user);
objectInputStream.close();
}
}
class User implements Serializable
{
private String nameString;//用户名
private String pswdString;//密码
public User(String nameString,String pswdString)
{
this.nameString = nameString;
this.pswdString = pswdString;
}
public String toString()
{
return "用户名：" + nameString + " 密码：" + pswdString;
}
}
import java.io.DataInputStream;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
public class TestDataStream {
/**
* @param args
* @throws FileNotFoundException
*/
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
FileOutputStream fileOutputStream = new FileOutputStream("a.txt");
DataOutputStream dataOutputStream = new DataOutputStream(fileOutputStream);
dataOutputStream.writeInt(100);
dataOutputStream.writeBoolean(true);
dataOutputStream.writeDouble(100.11);
dataOutputStream.close();
FileInputStream fileInputStream = new FileInputStream("a.txt");
DataInputStream dataInputStream = new DataInputStream(fileInputStream);
int i = dataInputStream.readInt();
boolean b = dataInputStream.readBoolean();
Double d = dataInputStream.readDouble();
System.out.println(i + "," + b + "," + d);
dataInputStream.close();
}
}