Online Reading: 02 - Arrays, Loops, Imports

Java Imports (ignore the parts about NetBeans)

Packages and Import

• Packages - Java classes can be grouped together in packages. Package name same as directory name containing the .java files.
• Package declaration - you can have import statements following the declaration, which will allow you to specify classes from other packages.
• Default package - a package that has omitted the package declaration.
• Package declaration syntax - statement order
  • Package statment
  • Imports
  • Class or interface definitions
• Imports: three options
  • JOptionPane class - is in the swing package, which is located in the javax package.
  • Wildcard character (*) - specifies that all classes with that package are available to your program.
  • Classes can be specified explicitly on import instead of using the wildcard character.
  • Can use class name without an import
• 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

Different types of loops in Java

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