201621123048 Java programming Tenth week of study summary

1. Study summary 1.1 This week summarize anomalies in the way you like (mind mapping or other).

2. Written work

This PTA job problem set anomaly

1. Common exceptions

Combined Topic 7-1 Answer

1.1 What exceptions do you often have in code that you have written before, and what do you need to capture (why)? What should be avoided?

Usually encountered more is arrayindexoutofboundsexception (Access array exception) and nullpointerexception (null pointer error), do not need to capture, because all is unchecked exception system will check the car, Check your code more to avoid

1.2 What kind of exception requires the user to be sure to use capture processing?

Checked exception exceptions must be captured for processing

2. Handle exceptions to make your program more robust

Topic 7-2

2.1 Experimental summary. And answer: How can you make your program more robust?

In this case, the string class is converted to an int row, the Try-catch exception is processed when the string is converted to a number, and the exception letter is output, and the program is added with exception handling to make the program more robust

3. Throw and throws

Topic 7-3
Read Integer.parsetint source code

3.1 Integer.parsetint There is a lot of code thrown out of the exception at the outset, what is the benefit of this practice?

The advantage is that programmers can know the cause of the exception, better read the program, make the program more robust

3.2 What information do you usually need to pass to the caller when you write your own program with 3.1 and analyze your own method of throwing an exception?

The thrown exception is illegalargumentexception, passing to the caller the cause of the exception error, such as the Begin>end, begin, and end relationships, to find a way to resolve the exception

4. Improve Arrayintegerstack with exception

Topic 6-3

4.1 In combination with 6-3 code, how does it benefit to use an exception-throwing method to represent a program run-time error? What is the advantage of returning an error value more than a simple one?

The advantage is a more intuitive understanding of why the program is wrong, if it is only a simple return error value, and can not know the error message, it is not easy to improve the program

4.2 If the inner code of a method throws an exception of type RuntimeException, does the method declaration use the throws keyword, and if the exception that is thrown by the method is declared using the throws keyword, what benefit can it bring us?

You can not use the throws keyword, because the runtimeexception type exception is not captured, if you use the advantage is that you can not need to Try-catch exception handling

5. Function questions-capture of multiple exceptions

Topic 6-1

5.1 Combined with 6-1 code, answer: If you can throw multiple exceptions in a try block, and there may be an inheritance relationship between exceptions, what do you need to be aware of when capturing?

Subclass exception to be placed before parent class exception

5.2 If you can throw multiple exceptions in a try block, what do you need to be aware of when using Java8 's multiple exception capture syntax?

A subclass exception must be caught before any of its parent classes, and if an exception is caught using a single catch block, the subclass exception is placed to the left of the parent exception

6. Add exception handling to the following code

byte[] content = null;
FileInputStream fis = new FileInputStream ("Testfis.txt");
int bytesavailabe = fis.available ();//Gets the number of bytes available for the file
if (bytesavailabe>0) {
Content = new byte[bytesavailabe];//Create an array that can hold the file size
Fis.read (content);//Read the contents of the file into an array
}
System.out.println (arrays.tostring (content));//print array contents

6.1 Correct the code and add the following functions. When the file cannot be found, you need to prompt the user not to find the file xxx, retype the file name, and then try to open it again. If it is another exception, prompt to open or read the file failed!.

Note 1: There are several methods inside that can throw an exception.
Feature 2: You need to add a finally close file. Regardless of whether the above code produces an exception, always be prompted to close the file ing. If closing the file fails, the prompt to close the file failed!

6.2 Combining the title set 6-2 code, what kind of action to put in the finally block? Why? What do I need to be aware of when closing resources using finally?

Because the finally block is carried out regardless of whether there is an exception capture, the operation to close the file is placed in Finall, the use of finally to close the resource will also produce an exception, so pay attention to exception handling

6.3 Use try-with-resources in Java7 to rewrite the above code to automatically close the resource. What are the benefits of this approach?

Using Try-with-resources to overwrite the above code automatically calls the close function to automatically close the resource and makes it easier

7. Object-oriented design job-Library management system (group completion, no more than 3 students per group)

Log in to lib.jmu.edu.cn to search for books. Then log in to the library information system to view my library. If you want to implement a book borrowing system, try using object-oriented modeling.

7.1 Who is the user of this system? 7.2 Main function modules (not too many) and the owner of each module. Next week everyone is going to submit their own module code and run the video. 7.3 Main class design and class diagram of the system (available) 7.4 How you plan to store library information, address information, reader information, and more. 3. Code Cloud and PTA

Topic Set: Exceptions

3.1. Code Cloud codes Submission record

In the Code cloud Project, select statistics-commits history-set time period, and then search for and

3.2 PTA Problem set complete situation diagram

Two graphs are required (1. Ranking chart. 2.PTA Submission list diagram)

3.3 Count the amount of code completed this week

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

Week Time	Number of rows	number of new rows	Number of files	number of new files
1	0	0	0	0
2	0	0	0	0
3	538	538	11	11
4	1262	724	25	14
5	1889	627	33	8
6	2313	424	39	6
7	3426	1113	59	20
8	4009	568	64	5
9	4689	680	72	8
10	5501	811	18	6

201621123048 Java programming Tenth week of study summary