201621123016 Java programming 12th Week of study summary

1. Summary of this week's study

1.1 Summarize multiple streams and file-related content in the way you like (mind mapping or other).

2. System-oriented integrated design-Library management system or shopping cart

Use streams and files to transform your library management system or shopping cart.
2.1 A brief description of how to use streams and files to transform your system. What is the format of the data in the file?

I use ObjectInputStream and Fileinputstream,objectoutputstream and FileOutputStream to read and save file information directly, The information stored in it is an array of type custom type user, in which the information for all users is saved.

2.2 Brief description of what interfaces and classes are used in the file reading and writing section of the system with the stream associated with the file? Why use these interfaces with classes?

The ObjectInputStream and Fileinputstream,objectoutputstream and FileOutputStream classes are used in the file, and these classes are used to store information about a user class directly. It is best to inherit the serializable interface in the class, which ensures that the file is read without errors.

2.3 Read and write file-related code. Critical lines need to be annotated.

3. Code Volume statistics

3.1 Count the amount of code completed this week

The weekly code statistics need to be fused into a single table.

Week Time	Total code Amount	New Code Volume	total number of files	number of new files
2	625	625	99	99
3	1429	804	113	14
4	3354	1925	223	110
5	3751	397	241	18
6	4369	31]	80	-161
7	4998	629	78	-2
8	5590	592	87	9
9	5751	161	89	2
11	6101	350	97	8
12	6495	394	104	7
13	6786	291	108	4

Option: 4. Flow and Document Learning Guide (the job content is all selected at the bottom) 1. Character stream with text file: Use PrintWriter (write) BufferedReader (read)

Writes the Student object (property: Int id, String name,int age,double grade) to the file Student.data, read from the file display.

1.1 Generated three student objects, using PrintWriter's Println method to write Student.txt, one student per line, and each student's attribute separated by |. Use scanner or BufferedReader to read the Student.txt data. (Key code, occurrence number)

This picture is cut in the school's lab, so it's not the same as other diagrams.

1.2 What is the size of the generated file (using the right-click File Properties view)? Analyze the file size

In which 1000000 of the user information is deposited to get a large size of 20.00Mb. This means that each line contains 21 bytes of sexual interest, one letter for a large size of one byte.

1.3 If the println method of PrintWriter is called, but not close at the back. What is the file size? Why?

The size of the file is 0. The file information is not saved to the file because it is not closed.

2. Buffer Stream

2.1 Use PrintWriter to write 10 million lines to a file (whatever it is), and then compare the speed (read only, not output) of reading data from the file using BufferedReader with scanner, which method is fast? Intercept the test source code, the number of the study. Please analyze the reasons in detail. Tip: You can use JUNIT4 to compare run times

This picture is cut in the school's lab, so it's not the same as other diagrams.

Using BufferedReader will save the contents of the file to the memory and then read, and scanner This is read directly from the file so use BufferedReader read faster.

2.2 Replace the PrintWriter with BufferedWriter to see if the speed of writing to the file has improved. Record the elapsed time of both. Try to analyze the reason.

3. Character encoding

3.1 Existing EncodeTest.txt file, contains some Chinese, the file is encoded using UTF-8. Use FileReader and BufferedReader to read the EncodeTest.txt text into and out. Do you have garbled characters? Why does it have garbled characters? How to solve? (Key code, occurrence number)

It could be the operating system. My output is fine.

Using GBK encoded output will cause an error.

Using UTF-8 to encode the output without error.

3.2 Writing method Convertgbk2utf8 (string src, string dst), you can convert the GBK encoded source file src to a UTF8 encoded destination file for DST.

201621123016 Java Programming 12th Week of study summary