Building Java Programs, 4th edition

Lab: Static Methods

Except where otherwise noted, the contents of this document are Copyright 2013 Stuart Reges and Marty Stepp.

lab document created by Marty Stepp, Stuart Reges and Whitaker Brand

Today's lab

Goals for today:

• practice using static methods to capture structure and redundancy

Static methods

Recall the syntax for writing a static method. Methods are useful for representing a program's structure and capturing common code to avoid redundancy:

public static void name() {
    statements;
}

Example:

public static void song() {
    System.out.println("This is the song that never ends,");
    System.out.println("Yes, it goes on and on, my friends.");
}

Exercise : Spikey

• Write a complete program named Spikey that produces the following output:

    \/
   \\//
  \\\///
  ///\\\
   //\\
    /\
  

  (Use only the material we have learned so far. You can check your output on the Output Comparison Tool web page.)

Exercise : Lanterns

• Write a complete program named Lanterns that produces the following output. Use static methods to capture structure and remove redundancy. (Check your output on the Comparison Tool.)

      *****
    *********
  *************
  
      *****
    *********
  *************
  * | | | | | *
  *************
      *****
    *********
  *************
  
      *****
    *********
  *************
      *****
  * | | | | | *
  * | | | | | *
      *****
      *****
  

Exercise : Spell your name

• Write a complete program that outputs your name in giant letters like the following:

  M     M    IIIII     SSSSS     PPPPPP
  MM   MM      I      S     S    P     P
  M M M M      I      S          P     P
  M  M  M      I       SSSSS     PPPPPP
  M     M      I            S    P
  M     M      I      S     S    P
  M     M    IIIII     SSSSS     P
  

  The giant letters should flow vertically. Use methods to avoid redundancy when the same giant letter appears multiple times in your name. (Use only the material from Chapter 1.)

Exercise : FightSong

Go, team, go!
You can do it.

Go, team, go!
You can do it.
You're the best,
In the West.
Go, team, go!
You can do it.

Go, team, go!
You can do it.
You're the best,
in the West.
Go, team, go!
You can do it.

Go, team, go!
You can do it.

The following program produces the output at left, but it has poor structure and redundancy. Download it and open it in jGRASP, then add at least two static methods.

• FightSong.java

continued on the next slide...

Exercise : FightSong, cont'd

Go, team, go!
You can do it.

Go, team, go! 
You can do it.
You're the best,
In the West.
Go, team, go!
You can do it.

Go, team, go! 
You can do it.
You're the best,
In the West.
Go, team, go!
You can do it.

Go, team, go!
You can do it.

Did you choose your methods well? Avoid the following pitfalls:

• Does the same println statement occur more than once in your code?
• Are there any println statements in the main method?
• Is your main method a good summary of the overall program? (If main is only 1-2 lines long, it is not a good summary.)
• Do you have any patterns of method calls that are repeated in the code?

Compare your method choice with your neighbor's. Discuss any different decisions you made and ask a TA if you have questions about them.