Importing 

 import java.util.ArrayList;

 (at the very top)

 nothing to import

 Creating 

 balloons = new ArrayList<Balloon>();

 someList = new ArrayList<SomeType>();

 creates an empty set of items

 balloons = new Balloon[ 20 ];

 someList = new SomeType[ 30 ];

 need to know the size in advance

 Indexing 

 0..size-1 

           __0_____1_____2_____3_____4__
 balloons: |_(*)_|_(*)_|_(*)_|_(*)_|_(*)_|

 0..size-1

           __0_____1_____2_____3_____4__
 balloons: |_(*)_|_(*)_|_(*)_|_(*)_|_(*)_|

 Size/Length 

 balloons.size()

 balloons.length

 Extracting Element 

 Balloon b = balloons.get( index ); 

 Balloon b = balloons[ index ]; 

 Updating Element 

 balloons.set( index, someBalloon ); 

 // differs from .add(...) -- replaces balloon
 // at given index, does not add new cell     

 balloons[ index ] = someBalloon; 

 Adding Elements 

 balloons.add( someBalloon );

 // balloon added to the end, size increased by 1

 not possible, initial size is fixed;

 Removing Elements 

 Balloon b = balloons.remove( index );

 // balloon at given index removed, size decreased by 1

 not possible, initial size is fixed;

double[] numbersList = { 1.2, 3.4, 5.6 };    
for ( int i = 0; i < numbersList.length; i = i + 1 )
{
    double curValue = numbersList[i];

    // do something with curValue
}

// this says: for each valid index:  
//                get the item at that index
//                do something with the item
//
// too much focus on index, all we want is the item

double[] numbersList = { 1.2, 3.4, 5.6 };
for ( double curValue : numbersList )
{
    // do something with value
}



// this says: for each item:
//                do something with the item
//
// this is much clearer, focus is on the item

// to get enhanced for-loop:
// * remove all index related components
// * move up the line that gets curValue
  
double[] numbersList = { 1.2, 3.4, 5.6 };    
for ( int i = 0; i < numbersList.length; i = i + 1 )
{
    ^-^-^-^-------- : ---------^-^-^
    double curValue = numbersList[i];

    // do something with curValue
}

double[] numbersList = { 1.2, 3.4, 5.6 };
for ( double curValue : numbersList )
{
    // do something with curValue
}

String[] wordsList = { "how", "are", "you" };    
for ( int i = 0; i < wordsList.length; i = i + 1 )
{
    String curWord = wordsList[i];

    // do something with curWord
}

String[] wordsList = { "how", "are", "you" };    
for ( String curWord : wordsList )
{
    // do something with curWord
}

ArrayList<String> wordsList = new ArrayList<String>();

// add some words to the list  

for ( int i = 0; i < wordsList.size(); i = i + 1 )
{
    String curWord = wordsList.get(i);

    // do something with curWord
}

ArrayList<String> wordsList = new ArrayList<String>();

// add some words to the list  

for ( String curWord : wordsList )
{
    // do something with curWord
}