Cwy of my classmates have been forced to do the same. From inside the book. Just a moment while we sign you in to your Goodreads account. Return to Book Page. I just started a 1st-year programming course which is taught in Java and uses this book, which has been ported from an earlier text for introductory programming in C. Thanks for telling essemtials about the problem.
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Reading Text Files You already know how to read data from a file and write data to a file, by using the system variables Console. However, this approach is limited. Java supports many file types. In this lab, you will learn about three of them: the TextInputStream and TextOutputStream classes that are part of the ccj package, and the RandomAccessFile class that is part of the standard java.
It turns out that text input and output is currently somewhat limited, difficult to use and inconsistent among the various Java versions. For that reason, you will use the ccj text stream classes in this lab. The operations of the standard Java stream classes are very similar, and the techniques that you use in this lab will help you using those stream classes as well.
To open a file, first define an object of type FileInputStream and then pass the file name to the constructor. After reading an input, always call the fail method. When it returns true, you have reached the end of input and you must ignore the return value of the last read command. To write output to a file, you make a TextOutputStream object and you write to it with the same print and println methods that you always used with System.
Write a program which compares the contents of two files. Have your program display the line number and text of the first pair of lines that differ. First, prompt the user for the names of the two files. Then open each file.
Remember to check for failure. Keep reading a line from each of them. Increment a line number counter. If both inputs fail, print a message indicating that both files are identical.
If one of the inputs fails and the other does not, print a message indicating which file is shorter, then exit. If the two input lines are different, print the line number counter and both input lines, then exit.
If the two input lines are identical, keep on reading. Reading Input Data in a Graphics Program Consider a graphics program that prompts the user to define shapes by selecting menu options and clicking on a window. Graphics can be stored in a variety of formats. Choosing the best format for a particular purpose involves factors such as speed, portability to different platforms and programs, and the storage space and transmission requirements.
In this lab exercise, we will use a simple text file containing lines of the form: Circle 1 3 5. When the program starts, all saved data are read in automatically from the file saved.
When the user adds more circles, then the new circles are appended to that file. Now implement the circle drawing program. Extra credit if you enhance it to handle both circles and lines! Command Line Arguments Extend your file comparison program in two ways. First, make it possible to specify the file names on the command line. Only ask the user for the file names when they are not specified. And support a command line flag to control the number of differences identified.
That is: differ -a file1. Random Access If a file stores records of fixed length, it is easy to locate any one of them.
If the records are also in a sorted order, for example employee records sorted by name, it is also possible to implement a fast search strategy called binary search. Rather than having to step through every record, you can eliminate half of the records remaining at each stage of the search because they are either too big or too small. Consider searching for the name "Mushroom" in the following listing.
Start in the middle, at record 7, "Lime". Compare it with the search term, "Mushroom". This time the middle among records 8 through 14 is record 11,"Pickle".
That leaves only records 8 through The middle record is 9. Here is the pseudocode to locate the value e, using binary search. Of course, you must use a data file that is sorted.
Computing concepts with Java 2 essentials
Computing Concepts with Java 2 Essentials