创建文件
//add file
File file =new File("E:\\java用文件","file.txt");
try{
file.createNewFile();
System.out.println("creat ok!");
}
catch (IOException e){
System.out.println("creat go die!");
e.printStackTrace();
}
删除文件
//delete
file.delete();
读取文件数据
//way first
File file =new File("E:\\java用文件","file.txt");
InputStream input = null;
byte b[] = new byte[(int)file.lenght()];
//根据文件的大小定义数组空间
try {
input = new FileInputStream(file);
input.read(b);
input.close();
}catch (IOException ee){
ee.printStackTrace();
}
//way second 常用
File file =new File("E:\\java用文件","file.txt");
InputStream input = null;
byte b[] = new byte[(int)file.length()];
int temp = 0;
int len = 0;
try{
input = new FileInputStream(file);
//使用FileInputStream为InputStream实例化
while((temp = input.read())!= -1)
{ //使用while循环读取文件内容，到达结尾是temp=-1
b[len] = (byte)temp;
len++;
}
input.close(); //关闭输入流
}catch(IOException ex){ //捕捉异常
ex.printStackTrace();
}
System.out.println(new String(b));
向文件写入内容
//会覆盖文件原本内容
File file =new File("E:\\java用文件","file.txt");
OutputStream out = null; //声明 OutputStream对象
String str = "Hello";
byte b[] = str.getBytes(); //把字符串转换为b数组
try{
out = new FileOutputStream(file);
//用 FileOutputStream实例化OutputStream
out.write(b); //写入数据
out.close(); //关闭输出流
System.out.println("write ok!");
}catch (IOException ev){ //捕捉异常
System.out.print("write go die!");
ev.printStackTrace(); //打印异常
}
//在末尾追加内容
//将传入FileOutputStream 构造方法中的参数append赋值为true即可
//public FileOutputStream(File dile,boolean append)throws
//FileNotFoundException
File file =new File("E:\\java用文件","file.txt");
OutputStream out = null; //声明 OutputStream对象
String str = "Hello";
byte b[] = str.getBytes(); //把字符串转换为b数组
try{
out = new FileOutputStream(file,true);
//用 FileOutputStream实例化OutputStream，添加true！！！
out.write(b); //写入数据
out.close(); //关闭输出流
System.out.println("write ok!");
}catch (IOException ev){ //捕捉异常
System.out.print("write go die!");
ev.printStackTrace(); //打印异常
}
//若想换行，可以在需要换行的字符串处添加转义字符"\r\n"即可
字符流
读取文件内容
File file =new File("E:\\java用文件","file.txt");
Reader read = null; //声明Reader对象
char c[] = new char[(int)file.length()];
try
{
read = new FileReader(file); //使用FileReader实例化Reader
read.read(c);
read.close();
}catch (IOException ee){
System.out.println("read go die !");
ee.printStackTrace();
}
System.out.println(c);
使用while方法读取
File file =new File("E:\\java用文件","file.txt");
Reader read = null; //声明Reader对象
char c[] = new char[(int)file.length()];
int temp = 0;
int len = 0;
try
{
read = new FileReader(file); //使用FileReader实例化Reader
while((temp = read.read())!=-1)
{ //用while读取 到达结尾时temp = -1
c[len] = (char)temp;
len++;
}
read.close();
}catch (IOException ee){
System.out.println("read go die !");
ee.printStackTrace();
}
System.out.println(c);
写入
//way1
File file =new File("E:\\java用文件","file.txt");
Writer out = null;
String str = "lllllll\r\n";
char c[] = str.toCharArray();
try{
out = new FileWriter(file,true);
out.write(c);
out.close();
System.out.println("write ok!");
}catch (IOException ee) {
System.out.print("write go die!");
ee.printStackTrace();
}
//way2
File file =new File("E:\\java用文件","file.txt");
Writer out = null;
String str = "lllllll\r\n";
try{
out = new FileWriter(file,true);
out.write(str);
out.close();
System.out.println("write ok!");
}catch (IOException ee) {
System.out.print("write go die!");
ee.printStackTrace();
}
字节流
字节输入流
File file = new File ("E:\\java用文件","file.txt");
InputStream input = null; //声明InputStream对象
byte b[]=new byte[(int)file.length()];
int temp = 0;
int len = 0;
try{
input = new FileInputStream(file);
//使用FileInputStream为 InputStream实例化
while((temp=input.read())!=-1)
{
b[len]=(byte)temp;
len++;
}
input.close();
}catch(IOException eq){
eq.printStackTrace();
}
System.out.println(new String(b));
字节输出流
File file = new File ("E:\\java用文件","file.txt");
OutputStream out = null;
String str = "el psy congroo";
byte b[] = str.getBytes();
try{
out = new FileOutputStream(file,true);
out.write(b);
out.close();
System.out.println("write ok!!!");
}catch(IOException ew){
ew.printStackTrace();
System.out.println("write go die");
}
对象序列化
对象序列化是将对象状态转换为可保持或传输的格式的过程
若需要某个对象能支持序列化机制，必须实现Serializable接口
class student implements Serializable{
String number;
String name;
String sex;
String birthday;
String department;
public student(String number,String name,String sex,String birthday,String department){
this.number = number;
this.name = name;
this.sex = sex;
this.birthday = birthday;
this.department = department;
}
}
对象输出流
File file =new File("E:\\java用文件","file.txt");
String name = jtname.getText();
String number = jtnumber.getText();
String sex = jtsex.getText();
String birthday = jtbirthday.getText();
String department = jtdepartment.getText();
student stu = new student(number,name,sex,birthday,department);
FileOutputStream fout = null;
ObjectOutputStream oos = null;
try{
fout = new FileOutputStream(file,true); //实例化文件输出流
oos = new ObjectOutputStream(fout); //实例化对象输出流
oos.writeObject(stu); //把对象写入输出流
oos.close(); //关闭对象输出流
}catch (IOException er){
er.printStackTrace();
System.out.println("writeobject go die");
}
对象输入流
File file =new File("E:\\java用文件","file.txt");
FileInputStream fis = null;
ObjectInputStream ois = null;
try{
fis = new FileInputStream(file);
ois = new ObjectInputStream(fis);
student stu = (student)ois.readObject(); //读取stu对象需要强制转换
ois.close();
jname.setText(stu.name);
jsex.setText(stu.sex);
jbirthday.setText(stu.birthday);
jdepartment.setText(stu.department);
}catch (IOException ex){ //捕捉IOException异常
ex.printStackTrace();
}catch(ClassNotFoundException we){ //捕捉ClassNotFoundException异常
we.printStackTrace();
}