Step 1: Getting Started At the beginning of each programming assignment you must have a comment block with following information: 1. /*-- 2. // AUTHOR: your name. 3. // FILENAME: title of the source file. 4. // SPECIFICATION: your own description of the program. 5. // FOR: CSE 110- Lab #10 6. // TIME SPENT: how long it took you to complete the assignment. 17. //--- *1 Step 2: Declaring a Class Lab10, the Main Method, and Variables 1. import java.io.BufferedReader; 2. import java.io.FileNotFoundException; 3. import java.io.FileReader; 4. import java.io.IOException; 5. 6. public class Lab10 7. { public static void main (String [] args) 8. 9. 18. 11. 12. // Step 2. Declaring Variables You Need 13. 14. 15. 16. 17. 18. 19. 20. // These constants are used to define 2D array and loop conditions final int NUM_ROWS = 4; final int NUM_COLS - 3; // A String variable used to save the lines read from input file } // End of main 21.) // End of class DELL 16. 17. 18. 19. 20. // A String variable used to save the lines read from input fil // --> } // End of main 21. } // End of class In Lab10, you would need several classes relevant to file IO, they are - FileReader: used to open a file and establish file input stream BufferedReader: used to "wrap" an input stream and enhance reading efficie FileNotFoundException: thrown when a file is not found (for FileReader) IOException: thrown when some I/O error occurs (for BufferedReader) All of these classes are placed in the package "java.io". At the top of your main function, you can declare variables you need. You might need local variables of the following types: A String used to store one line read by BufferedReader The two constants NUM ROWS and NUM_COLS are defined for the array size and file reading. A String used to store one line read by BufferedReader The two constants NUM_ROWS and NUM_COLS are defined for the array size and f reading. You can declare extra variables if needed. Step 3: Declaring the Array for File Input 1. *** 2. // Step 3. Declare the Array for File Input 3. // Please involve the two constants NUM ROWS and NUM COLS in the 4. // constructor. 15. // --> Make a NUM_ROWS by NUM_COLS 2D String array. Because an array in Java is an object, we would use the keyword "new" and its constructor to instantiate it, just like our Scanner, Person, Student, and Employee in the past. Step 4: Preparing an Input File 1. // 2. // Step 4: Preparing an Input File 3. // 4. // Make a text file and write 12 strings in it, one string in each line, 5. // and then save it in the folder where your Lab10.java is. 6. // 7. // Note: If you are using Eclipse, please save the file out of "src" 8. // folder. 9. 11 18. // 11111 NO CODE REQUIRED IN THIS SECTION 111 DELL you are using Eclipse, please save the file out of "src" E 8. // folder. 9. // 10. // !!!!! NO CODE REQUIRED IN THIS SECTION !!!!! NO CODE IS REQURED IN THIS STEP. Please create a text file containing 12 lines as follows: 1. January 2. February 3. March 4. April 5. May 6 June 7. July B. August 9. September 18. October DELL 11. November 12. December You can name it whatever you like (ex. Input.txt, my_input_file.txt,...) When you read the file at Step 5, you will need the filename. Note: If you are using TextPad, please place the file at the same place where the Lab10.java is. If you are using Eclipse, this input file should be places "outside" of the "src" folder but inside the project. Step 5: Reading the File 1. 2. try { 3. 4. 6. 7. // Instantiate a FileReader object to open the input file // Note: "filename" should match the input file you made in Step 4 FileReader fr = new FileReader("filename"); 5. NY BufferedReader is for efficient reading of characters 8. BufferedReader bfReader = new BufferedReader(fr); 9. 10. // Just like scanner.nextLine(), whenever you invoke .readLine() 11. // on BufferedReader, it will read a single line from the file. 12. 13. // // As we have determined the number of lines in our file, we will // use constants to define the loop conditions for (int i=0; i <= NUM_ROWS - 14. 15. 1; i++) 16. 17. 18. for (int j=0; j <- NUM_COLS 1; j++) 19. 28. 21. // Read a line from the file // Please invoke .readLine() on the BufferedReadere bfReader // and save the returned value to the element at array position (i, j) // --> } 24. } // It is very important to close your file after reading is done bfReader.close(); 22. 23. 25. 26. 27. 28. 29. 36. { 31. 32. catch (FileNotFoundException e) System.err.println("File not found"); DELL catch (IOException e). System.err.println("I/O error occurs"); 33. 34. { 35. 36. } Note: All code in this step should be wrapped inside a "try" statement and two "catch" statements follow for exception handling. For more details, please refer the lecture slide or the textbook. In this step, we will read the file created in Step 4 by our program. Like user input, a file is handled as "input stream" in Java. Java provides many tools for you to establish input stream on a file and read data from it. Here we will use 1) FileReader to open a file and build input stream and 2) BufferedReader to improve reading efficiency. There are two steps here, first we need to open a file by using FileReader class: h. FileReader fr = new FileReader("filename"); Here the String "filename" should be replaced by the filename you created in Step 4. For example, if your input file is called "input.txt", we use "input.txt" as the parameter of this constructor. If your file reader cannot find the file, it will throw "FileNotFoundException". After instantiating FileReader, we need a BufferedReader to do efficient reading: 11. BufferedReader bfReader - new BufferedReader(fr); The parameter of this constructor is the file reader we just created. Now we are ready to read data from the file. Remember when we read input from the user, we use scanner.nextLine(). We can use the similar method defined in BufferedReader to read one line in the file. It would be like DELL ve use scanner.nextLine(). We can use the similar method defined in BufferedReader to m one line in the file. It would be like h. bfReader.readLine(); This statement returns one line in the file as a single String. You can save this String to the place you like by "=" assignment operator. The file reading is controlled by "file pointer", which points to the line your reader currently read on. When you call readLine(), this pointer will move to the next line. So your program can invoke .readLine() multiple times by loop and read the whole file. We have placed the "for" loops you need in the template file (showed above). Step 6: Print the Elements in the 2D Array Finally, please print the content in your 2D array where the input data is saved. // Step 6. Print the Elements in the 20 Array B. 4 for (int 10; i < MUM ROWS 21 300) 5. for (int 1-1 - IAM COLS EX DELL 13 Step 6: Print the Elements in the 2D Array Finally, please print the content in your 2D array where the input data is saved. 1. // 2. // Step 6. Print the Elements in the 2D Array 3. 4. for (int i = 0; i <= NUM ROWS 1; i++) 5. { 6. 7. 8. 9. 10. 11. 12. } for (int i = 0; i <- NUM COLS 1; 1++) // Print the element at position (1, 1) // --> System.out.println(); Sample Output DELL 1. // 2. // Step 6. Print the Elements in the 2D Array 3. A 4. for (int i = 0; i <= NUM ROWS - 1; i++) 5. { 6. for (int i = 0; i <= NUM COLS 1; i++) - 7. { 8. 9. 10. } 11. // Print the element at position (i, j) // --> System.out.println(); 12. } Sample Output This sample output is based on an input file "input.txt" with the following content: 1. 2. January February 3. March 4. April 5. May 6. June 7. July 8. August 9. September 10. October 11. November 12. December Below is an example of what your output should roughly look like when this lab is completed. Text in RED represents user input. The content in input.txt January February March April May June July August October November September December DELL