字符流
字符流，以字符为单位读写数据
Reader
转换流 InpuStreamReader
FileReader
BufferedReader
Writer
转换流 OutStreamWriter
FileWriter
BufferedWriter
Reader 的基本方法 读取一个字符并以整数的形式返回, 如果返回-1已到输入流的末尾。
Writer 的基本方法向输出流中写入一个字符数据,该字节数据为参数b的16位
FileReader&&FileWriter
public static void main(String[] args) throws IOException {
FileReader reader = new FileReader("D:\\test.txt");
FileWriter writer = new FileWriter("D:\\test1.txt");
/*int c = ' ';
while((c= reader.read())!=-1){
System.out.println((char)c);
writer.write(c);
}*/
//读取为字符类型数组
char[] c = new char[5];
int length;
while((length= reader.read(c))!=-1){
System.out.println(length);
writer.write(c,0,length);
}
writer.close();
reader.close();
}
BufferedReader&&BufferedWriter
FileWriter方法中有字符拼接，写入时不会覆盖原来的内容，会在后面继续拼接
BufferedWriter中readLine();方法,实现了每次可以读取文件中一行的功能
public static void main(String[] args) throws IOException {
FileReader reader = new FileReader("D:\\test.txt");
BufferedReader breader = new BufferedReader(reader);
// FileWriter方法中有字符拼接，写入时不会覆盖原来的内容，会在后面继续拼接
FileWriter writer = new FileWriter("D:\\test1.txt", true);
BufferedWriter bwriter = new BufferedWriter(writer);
//读完时返回null；
//breader.readLine()一次读一行数据
/*System.out.println(breader.readLine());
System.out.println(breader.readLine());
System.out.println(breader.readLine());*/
String line = null;
while ((line = breader.readLine()) != null) {
bwriter.write(line);//一次一行写入
bwriter.newLine();//新的一行
}
bwriter.flush();
bwriter.close();
breader.close();
}
Print打印流
打印流:单向的从程序中向外输出数据
PrintWriter:打印字符流
案例: 例如 从服务器端向 客户端浏览器 输出网页信息.
public static void main(String[] args) throws FileNotFoundException {
PrintWriter out = new PrintWriter("E:\\demo.html");
out.println("<h1>这是从服务器端响应回来的数据</h1>");
out.println("<h1>这是从服务器端响应回来的数据</h1>");
out.write("<h2>这是从服务器端响应回来的数据</h2>");
out.print(true);// print底层使用的还是write() 只是重载了多个,可以处理多种的数据类型
out.close();
}
对象输入输出流(对象序列化和反序列化)
对象输入输出流
对象:内存中的对象
为什么要将对象输出?
内存中的数据在电脑关闭,服务器停止时数据就会消失
有时候需要将这些数据保存起来
对象的输出流： ObjectOutputStream
对象的输入流: ObjectInputStream
public static void main(String[] args) throws IOException, ClassNotFoundException {
// 对象的序列化
FileOutputStream out = new FileOutputStream("D:\\demo.txt");
//ObjectOutputStream中用writeObject()方法可以直接将对象保存到输出流中。
ObjectOutputStream oout = new ObjectOutputStream(out);
String s ="abc";
Date date =new Date();
oout.writeObject(s);
oout.writeObject(date);
oout.close();
//反序列化
FileInputStream in = new FileInputStream("D:\\demo.txt");
//在ObjectInputStream 中用readObject()方法可以直接读取一个对象
ObjectInputStream oin =new ObjectInputStream(in);
String s =(String) oin.readObject();
Date date = new Date();
System.out.println(s);
System.out.println(date);
oin.close();
}
新建Student类
/*
需要被序列化类的对象,此类必须要实现Serializable接口
*/
public class Student implements Serializable {
//会自动为类生成一个 默认ID号,当此类中的内容发生修改后,id号会发生变化
//实用工具生成一个序列化ID号,这样类发生修改后,此ID依然不会改变
private static final long serialVersionUID = -7119195593092378008L;
int num;
String name;
//被transient修饰的属性,不能被序列化
transient String adress;
public Student(int num, String name,String adress) {
this.num = num;
this.name = name;
this.adress= adress;
}
@Override
public String toString() {
return "Student{" +
"num=" + num +
", name='" + name + ",adress="+adress+'\'' +
'}';
}
}
public static void main(String[] args) throws IOException, ClassNotFoundException {
FileOutputStream fos = new FileOutputStream("D:\\demo.txt");
ObjectOutputStream oos = new ObjectOutputStream(fos);
Student stu = new Student(12,"jim","陕西省");
oos.writeObject(stu);
oos.close();
}
public static void main(String[] args) throws IOException, ClassNotFoundException {
FileInputStream in = new FileInputStream("D:\\demo.txt");
ObjectInputStream oin = new ObjectInputStream(in);
Student student = (Student)oin.readObject();
System.out.println(student);
oin.close();
}