ch7_solutions.md

Ch7 Exercise Solutions

1. gchen213@C02VJ01NHTDD:temp$ ls
   MyPackage.scala Tester1.scala   Tester2.scala
   gchen213@C02VJ01NHTDD:temp$ cat MyPackage.scala 
   package com {
     package horstmann {
       object Horstmann {
         val author = "Horstmann"
       }
       package impatient {
         object Impatient {
           val patienceLevel = 0
         }
       }
     }
   }
   
   gchen213@C02VJ01NHTDD:temp$ cat Tester1.scala 
   package com.horstmann.impatient
   class Tester1 {
     val horstmann = Horstmann.author
     val impatient = Impatient.patienceLevel
   }
   
   gchen213@C02VJ01NHTDD:temp$ cat Tester2.scala 
   package com
   package horstmann
   package impatient
   
   class Tester1 {
     val horstmann = Horstmann.author
     val impatient = Impatient.patienceLevel
   }
   
   gchen213@C02VJ01NHTDD:temp$ scalac MyPackage.scala && ls
   MyPackage.scala Tester1.scala   Tester2.scala   com
   gchen213@C02VJ01NHTDD:temp$ scalac Tester1.scala 
   Tester1.scala:3: error: not found: value Horstmann
     val horstmann = Horstmann.author
                     ^
   one error found
   gchen213@C02VJ01NHTDD:temp$ scalac Tester2.scala 
   gchen213@C02VJ01NHTDD:temp$ 

2. Skipped. Exercise instructions unclear.
3. Refer to src/main/scala/Ch7Ex1Random.scala for solution and src/test/scala/Ch7Tests for tests.
4. Section 7.5 states,

A package can contain classes, objects, and traits, but not the definitions of functions or variables. That's an unfortunate limitation of the Java virtual machine. It would make more sense to add utility functions or constants to a package than to some Utils object. Package objects address this limitation.

5. The method is package private to the package com. In general this a useful language feature which achieves the same effect as Java's package private class members. However, in this particular cse it is not very useful, since the package com is a top level package.
6. Refer to src/main/scala/Ch7Helpers.scala for solution and src/test/scala/Ch7Tests for tests.
7. Refer to src/main/scala/Ch7Helpers.scala for solution and src/test/scala/Ch7Tests for tests.
8. Terrible idea as you will be importing the entire Java universe into your namespace. This would be a terrible idea even if it were a Java program, not to mention a Scala one, since you miss the whole point of namespaces if you simply import the whole universe into the namespace.
9. Skipped. TODO: finish this exercise
10. Skipped. TODO: finish this exercise