SINGLE-DIMENSIONAL ARRAYS - Introduction to Java Programming: Comprehensive Version - page 251

accessed simply via the index. The following code prompts the user to enter a month
number and displays its month name:

String[] months = { "January" , "February" , ..., "December" };
System.out.print( "Enter a month number (1 to 12): " );
int monthNumber = input.nextInt();
System.out.println( "The month is " + months[monthNumber - 1 ]);

If you didn't use the months array, you would have to determine the month name using
a lengthy multi-way if-else statement as follows:

if (monthNumber == 1 )
System.out.println( "The month is January" );
else if (monthNumber == 2 )
System.out.println( "The month is February" );
...
else
System.out.println( "The month is December" );

7.2.7 Foreach Loops
Java supports a convenient for loop, known as a foreach loop , which enables you to traverse
the array sequentially without using an index variable. For example, the following code dis-
plays all the elements in the array myList :

for ( double e: myList) {
System.out.println(e);
}

You can read the code as “for each element e in myList , do the following.” Note that the
variable, e , must be declared as the same type as the elements in myList .
In general, the syntax for a foreach loop is

for (elementType element: arrayRefVar) {
// Process the element

}

You still have to use an index variable if you wish to traverse the array in a different order or
change the elements in the array.

Caution
Accessing an array out of bounds is a common programming error that throws a runtime
ArrayIndexOutOfBoundsException . To avoid it, make sure that you do not use
an index beyond arrayRefVar.length - 1 .
Programmers often mistakenly reference the first element in an array with index 1 , but
it should be 0 . This is called the off-by-one error . Another common off-by-one error in
a loop is using <= where < should be used. For example, the following loop is wrong.

ArrayIndexOutOfBounds-
Exception

off-by-one error

for ( int i = 0 ; i <= list.length; i++)
System.out.print(list[i] + " " );

The <= should be replaced by < .

7.1

✓ ✓

How do you declare an array reference variable and how do you create an array?

Check

7.2

When is the memory allocated for an array?

Point