Packages and Import

Packages and Import

A Package is the same as directory

package declarations must be the first statements
after importing a package you can specify classes from that package
For small programs it's common to omit package declaration, although it is not recommended.
The wildcard character (*) is used to specify that all classes with that package are available to your program.
you can specify the exact class that you want to use instead of *
Common imports:
- import java.awt.\*; Common GUI elements.
- import java.awt.event.\*; The most common GUI event listeners.
- import javax.swing.\*; More common GUI elements. Note "javax".
- import java.util.\*; Data structures (Collections), time, Scanner, etc classes.
- import java.io.\*; Input-output classes.
- import java.text.\*; Some formatting classes.
- import java.util.regex.\*; Regular expression classes.
imports doesn't make the file larger
using \* in the import prevents accidentally defining classes with names that conflict with the standard library names
import with \* doesn't include any of the subpackages
Static imports in Java 5 leads to name pollution and confusion about which class constants come from.

A Guide to Java Loops

A Guide to Java Loops

Looping in programming langauges is a feature that facilitates the execution of a set of instructions until the controlling Boolean-expression evaluates to false.

Types of loops

For loop - allows you to repeat certain operations by incrementing and evaluating a loop counter
While loop - repeats a statement or a block of statements while its controlling Boolean-expression is true
Do-While loop - like a while loop, but the first condition evaluation happens after the first iteration of the loop