Introduction to Arrays Chapter 10

10 What is an array? An array is an ordered collection that stores many elements of the same type within one variable name. Elements are the items in an array. Each element is identified with an index number. Index numbers always start at 0 for the first element.

10 Declaring Arrays Identify type of array Use square brackets int[] myArray; Declares an array of int values

10 Instantiating Arrays Use the new keyword Identify number of elements myArray = new int[1000]; Instantiates myArray with 1000 elements You can declare and instantiate in one line int[] myArray = new int[1000];

10 Putting Values in the Array Use the index operator to assign a value at a particular place in the array. myArray[10] = 100; Assigns the value 100 to the 10 th element in the array Most programs use a for loop to iterate the array.

10 Initializing the Array You can initialize the array with values at the same time the array is created. int[] myArray = {1, 2, 3, 4, 5};

10 Determining the Length of the Array Use the length property to find the number of elements in the array. System.out.println(myArray.length); Displays the length of the array in the console For ( int i = 0; i < myArray.length; i++ ); Uses the length property to set up the for loop

10 Passing by Value Intrinsic types are passed to methods by value. A copy of the value is passed. The original value is unchanged.

10 Passing by Reference Objects are passed to methods by reference. The reference points to the original object. A change to the object affects the object in the calling method.

10 Passing Arrays to Methods An array is an object type. Passed by reference Elements of arrays are not necessarily passed by reference. Depends on the underlying element type Extracting int elements from an array and passing them to a method passes them by value

10 Using Polymorphic Objects in an Array An array can hold objects that: Derive from the same base class Implement a common interface