一,File创建文件
File file = new File("D:" + File.separator + "yi.txt");
代码示例:
package com.hbut.io; import java.io.File;
import java.io.IOException; public class FileDemo { public static void main(String[] args) {
File file = new File("D:" + File.separator + "yi.txt");
if (file.exists()) {
file.delete();
System.out.println("文件已存在");
} else {
try {
boolean states=false;
states = file.createNewFile();
if(states==true)
{
System.out.println("文件创建成功");
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
二,OutputStream(字节流)写入文件
out= new FileOutputStream(file);//获取实际的字节流输出对象,内容覆盖
String info="hello";//要输入的内容
byte[] b=info.getBytes();//将字符转化为字节数组
out.write(b);
代码示例
package com.hbut.io; import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream; public class OutputDemo {
public static void main(String[] args) {
File file = new File("D:" + File.separator + "yi.txt");//指定要写入的文件
OutputStream out=null;//定义字节流输出对象
try {
out= new FileOutputStream(file);//获取实际的字节流输出对象,内容覆盖
} catch (FileNotFoundException e) {
e.printStackTrace();
}
String info="hello";//要输入的内容
byte[] b=info.getBytes();//将字符转化为字节数组
try {
out.write(b);
} catch (IOException e) {
e.printStackTrace();
}
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
三,InputStream(字节流)读出文件
InputStream In = null;// 定义字节流输入对象
In = new FileInputStream(file);// 获取实际的字节流输入对象
byte[] b = new byte[1024];// 开辟空间,读取内容
len = In.read(b);// 读取
System.out.println(new String(b, 0, len));//输出读取的内容
代码示例
package com.hbut.io; import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream; public class InputStreamDemo {
public static void main(String[] args) {
File file = new File("D:" + File.separator + "yi.txt");// 指定要读取的文件
InputStream In = null;// 定义字节流输入对象
try {
// out= new FileOutputStream(file,true);//是否字节追加函数
In = new FileInputStream(file);// 获取实际的字节流输入对象
} catch (FileNotFoundException e) {
e.printStackTrace();
}
int len = 0;// 输入数组长度
byte[] b = new byte[1024];// 开辟空间,读取内容
// byte[] b=new byte[(int)file.length()];//根据文件大小开辟空间
try {
len = In.read(b);// 读取
} catch (IOException e1) {
e1.printStackTrace();
}
try {
In.close();
} catch (IOException e) {
e.printStackTrace();
}
System.out.println(new String(b, 0, len));
}
}
四,Writer(字符流)写入文件
Writer write = null;// 定义字符输出流
write = new FileWriter(file);
String infor = "hello,WriterDemo";//即将写入文件的信息
write.write(infor);//写入文件
代码示例
package com.hbut.io; import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer; public class WriterDemo {
public static void main(String[] args) {
File file = new File("D:" + File.separator + "WriterDemo.txt");// 指定要写入的文件
Writer write = null;// 定义字符输出流
try {
write = new FileWriter(file);
} catch (IOException e) {
e.printStackTrace();
}
String infor = "hello,WriterDemo";
try {
write.write(infor);
} catch (IOException e) {
e.printStackTrace();
}
try {
write.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
五,Reader(字符流)读出文件内容
Reader read = null;// 定义字符输入流
read = new FileReader(file);
char[] b=new char[1024];//设置字符的长度
int len=read.read(b);//文件内容读入到 b[]
System.out.println(new String(b));
代码示例
package com.hbut.io; import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader; public class ReaderDemo {
public static void main(String[] args) {
File file = new File("D:" + File.separator + "yi.txt");// 指定要读出的文件
Reader read = null;// 定义字符输入流
try {
read = new FileReader(file);
} catch (IOException e) {
e.printStackTrace();
}
char[] b=new char[1024];//设置字符的长度
try {
int len=read.read(b);
System.out.println(new String(b));
} catch (IOException e) {
e.printStackTrace();
}
try {
read.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}