Questions and Exercises: Implementations

Questions

  • You plan to write a program that uses several basic collection interfaces: Set , List , Queue , and Map . You're not sure which implementations will work best, so you decide to use general-purpose implementations until you get a better idea how your program will work in the real world. Which implementations are these?

  • If you need a Set implementation that provides value-ordered iteration, which class should you use?

  • Which class do you use to access wrapper implementations?

Exercises

  • Write a program that reads a text file, specified by the first command line argument, into a List . The program should then print random lines from the file, the number of lines printed to be specified by the second command line argument. Write the program so that a correctly-sized collection is allocated all at once, instead of being gradually expanded as the file is read in. Hint: To determine the number of lines in the file, use java.io.File.length to obtain the size of the file, then divide by an assumed size of an average line.

Check your answers.