Documentation

The Java™ Tutorials
Hide TOC
Questions and Exercises
Trail: Collections
Lesson: Implementations

Questions and Exercises: Implementations

Questions

  1. 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?
  2. If you need a Set implementation that provides value-ordered iteration, which class should you use?
  3. Which class do you use to access wrapper implementations?

Exercises

  1. 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.


Previous page: Summary of Implementations
Next page: Algorithms