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Chapter overview This chapter focuses on
Array declaration and use
Bounds checking and capacity
Arrays storing object references
Variable length parameter lists
Multidimensional arrays
The ArrayList class
Two-dimensional arrays
A one-dimensional array stores a list of element
A two dimensional array Can be thought of as a table of elements
With rows and columnsone
dimensiontwo
dimensions
Two dimensional arrays: declaration To be precise, in JAVA
A two-dimensional array is an array of arrays
A two-dimensional array is declared by specifying the size of each dimension
An array element is referenced using two index values
The array stored in one row Can be specified using one index
int[][] scores = new int[12][50];
value = scores[3][6]
Two-dimensional arrays: example
See TwoDArray.java
See SodaSurvey.java
Expression Type Description
table int[][] 2D array of integers, or
array of integer arrays
table[5] int[] array of integers
table[5][12] int integer
Chapter overview This chapter focuses on
Array declaration and use
Bounds checking and capacity
Arrays storing object references
Variable length parameter lists
Multidimensional arrays
The ArrayList class
The ArrayList class
The ArrayList class is part of java.util
Can store a list of values and reference each one using a numeric index
Dynamically grows and shrinks as needed Adjusting its capacity as necessary
However, you cannot use the brackets syntax With an ArrayList object
ArrayList elements
ArrayList is not declared to store a particular type
any type of object can be added to an ArrayList
stores references to different types of objects
If a primitive value must be stored in an ArrayList Use the appropriate wrapper class
Arraylist: inserting and removing elements
Elements in an ArrayList Can be inserted or removed
with a single method invocation
When an element is inserted Other elements move aside to make room
When an element is removed The list collapses to close the gap
The indexes of elements adjust accordingly
Specifying an ArrayList element type
See Beatles.java
we can also define An ArrayList object to accept a particular object type
The following declaration creates an ArrayList object that only stores Family objects
ArrayList<Family> reunion = new ArrayList<Family>
Methods defined in ArrayList
boolean add(Object obj) Inserts the specified object to the end of the list
object remove(int index) Removes the element at specified index in the list
void add(int index, Object obj) Inserts the specified object into list at specified index
int indexOf(Object obj) Returns the index of 1st occurrence of the specified
object