这个课程的参考视频和图片来自youtube。
主要学到的知识点有：
We want to handle the bad Error. (e.g bad input / bugs in program)
1. File() : A Java representation of a file.
File file = new File("test.txt");
2. PrintWriter() : Write to a file.
- Write string into the file.
// Write 2 lines(Johnson, 26) into the test.txt file. (If not exist then create one, otherwise will overwrite it.)
PrintWriter output = new PrintWriter(file);
output.println("Johnson");
output.println("26");
output.close();
3. Scanner() : Read from a file.
- Read string from the file.
Scanner input = new Scanner(file);
String name = input.nextLine();
int age = input.nextLine();
4. Object Serialization : convert an object into a series of bytes so they can be written to disk
- Serialization: Object to Disk
- Deserialization: Disk to Object
- In order to use the seialization, we need to add implement Serializable in the class definition (the contens will be in a binary format)
public class Student implements Serializable {
- FileInputStream & ObjectInputStream
Read from a file as bytes and deserialize a data input stream back into an object
// deserialize the collection of students
FileinputStream fi = new FileinputSream(file);
ObjectInputStream input = new ObjectOutputStream(fi);
while(input.hasNext()){
Student s =(Student) input.readObject();
students.add(s);
}
input.close();// Important when writing a file as operating system will deny other programs access until the file is closed
fi.close();
- FileOutputStream & ObjectOutputStream
Write to a file as bytes and serialize an object into a data input stream
// serialize the collection of students
FileOutputStream fo = new FileOutputSream(file);
ObjectOutputStream output = new ObjectOutputStream(fo);
for(Student s: students){
output.writeObject(s);
}
output.close();// Important when writing a file as operating system will deny other programs access until the file is closed
fo.close();