1.4-1_Understanding Package Declarations and Imports

Question 1

How are grouped Java classes?

Answer 1

into packages

Question 2

What does the import statement does?

Answer 2

The import statement tells the compiler which package to look in to find a class.

Question 3

[WildCards] What is the wildcard symbol?

Answer 3

The * is the wildcard, that matches all classes in the package.

Question 4

[WildCards] Does the wildcard slowdown your execution?

Answer 4

Including wildcard on import doesn’t slow down your program execution

Question 5

Which package is automatically imported?

Answer 5

Everything in java.lang is automatically considered to be imported.

Question 6

When is required to import packages?

Answer 6

✅ When referencing a class which is in another package. 
✅ When you're using classes from different packages but have the same name.
⚠️Importing a class that is in the same package as the class importing it. (Is a redundancy)

Question 7

[WildCards] Does a wildcard in a simple import matches also fields and methods?
import {package};

Answer 7

No, this is only achievable via static imports.
With a simple import You cannot import methods only class names.

Question 8

Could you have multiple wildcards in an import statement?

Answer 8

No, You can only have one wildcard and it must be at the end.
✅ import java.nio.;
❌ import java.nio..*;

Question 9

[Naming Conflicts] What does Naming conflicts mean when importing classes?

Answer 9

When the class is found in multiple packages, Java gives you a compiler error.

Question 10

[Naming Conflicts] Is there any precedence regarding wildcards and naming conflicts?

Answer 10

If you explicitly import a class name, it takes precedence over any wildcards import.
import java.util.*;
import java.sql.Date;
java.sql.Date will take precedence in these imports.

Question 11

What options do you have when you need to use 2 classes with the same name?

Answer 11

o  You can pick one to use in the import and use the other’s fully qualified class name.
o  Or you could have neither with an import and always use the fully qualified class name.