Chapter 7 Arrays and Array Lists - Frontier Central School

100 Pages·2015·1.12 MB·English

Chapter 7 – Arrays and Array Lists
Big Java by Cay Horstmann
Copyright © 2009 by John Wiley & Sons. All rights reserved.
Jeff Staruch Wednesday, May 27, 2015 at 9:30:17 AM Eastern Daylight Time 34:15:9e:2f:35:24
Chapter Goals

(cid:72) To become familiar with using arrays and array lists

(cid:72) To learn about wrapper classes, auto-boxing and the

generalized for loop
(cid:72) To study common array algorithms

(cid:72) To learn how to use two-dimensional arrays

(cid:72) To understand when to choose array lists and arrays in your

programs
(cid:72) To implement partially filled arrays

T To understand the concept of regression testing

Big Java by Cay Horstmann
Copyright © 2009 by John Wiley & Sons. All rights reserved.
Jeff Staruch Wednesday, May 27, 2015 at 9:30:17 AM Eastern Daylight Time 34:15:9e:2f:35:24
Arrays
(cid:72) Array: Sequence of values of the same type

(cid:72) Construct array:

new double[10]
(cid:72)  Store in variable of type :
double[]
double[] data = new double[10];
(cid:72) When array is created, all values are initialized depending on

array type:
(cid:72) Numbers:

0
(cid:72) Boolean:

false
(cid:72) Object References:

null
Big Java by Cay Horstmann
Copyright © 2009 by John Wiley & Sons. All rights reserved.
Jeff Staruch Wednesday, May 27, 2015 at 9:30:17 AM Eastern Daylight Time 34:15:9e:2f:35:24
Arrays
Big Java by Cay Horstmann
Copyright © 2009 by John Wiley & Sons. All rights reserved.
Jeff Staruch Wednesday, May 27, 2015 at 9:30:17 AM Eastern Daylight Time 34:15:9e:2f:35:24
Arrays
Use to access an element:
[]
values[2] = 29.95;
Big Java by Cay Horstmann
Copyright © 2009 by John Wiley & Sons. All rights reserved.
Jeff Staruch Wednesday, May 27, 2015 at 9:30:17 AM Eastern Daylight Time 34:15:9e:2f:35:24
Arrays
(cid:72) Using the value stored:

System.out.println("The value of this data item is "
+ values[2]);
(cid:72) Get array length as (Not a method!)

values.length
(cid:72) Index values range from to

0 length - 1
(cid:72)  Accessing a nonexistent element results in a bounds error:

double[] values = new double[10];
values[10] = 29.95; // ERROR
(cid:72) Limitation: Arrays have fixed length

Big Java by Cay Horstmann
Copyright © 2009 by John Wiley & Sons. All rights reserved.
Jeff Staruch Wednesday, May 27, 2015 at 9:30:17 AM Eastern Daylight Time 34:15:9e:2f:35:24
Declaring Arrays

Big Java by Cay Horstmann
Copyright © 2009 by John Wiley & Sons. All rights reserved.
Jeff Staruch Wednesday, May 27, 2015 at 9:30:17 AM Eastern Daylight Time 34:15:9e:2f:35:24
Arrays
Syntax 7.1
Big Java by Cay Horstmann
Copyright © 2009 by John Wiley & Sons. All rights reserved.
Jeff Staruch Wednesday, May 27, 2015 at 9:30:17 AM Eastern Daylight Time 34:15:9e:2f:35:24
Self Check 7.1
What elements does the data array contain after the following
statements?
double[] values = new double[10];
for (int i = 0; i < values.length; i++)
values[i] = i * i;
Answer: 0, 1, 4, 9, 16, 25, 36, 49, 64, 81, but not 100
Big Java by Cay Horstmann
Copyright © 2009 by John Wiley & Sons. All rights reserved.
Jeff Staruch Wednesday, May 27, 2015 at 9:30:17 AM Eastern Daylight Time 34:15:9e:2f:35:24
Self Check 7.2
What do the following program segments print? Or, if there is an
error, describe the error and specify whether it is detected at
compile-time or at run-time.

a) double[] a = new double[10];
System.out.println(a[0]);

b) double[] b = new double[10];
System.out.println(b[10]);

c) double[] c;
System.out.println(c[0]);
Answer:
a) 0

b) a run-time error: array index out of bounds

c) a compile-time error: c is not initialized

Big Java by Cay Horstmann
Copyright © 2009 by John Wiley & Sons. All rights reserved.
Jeff Staruch Wednesday, May 27, 2015 at 9:30:17 AM Eastern Daylight Time 34:15:9e:2f:35:24