Ch 9: Arrays

Question 1

what are the individual memory locations in an array called

Answer 1

elements

Question 2

several consecutive memory locations of the same data type under one name is

Answer 2

an array

Question 3

number of elements in an array is called

Answer 3

size or length of the array

Question 4

program can refer to an individual element of an array using the array name followed by the element’s number which is called

Answer 4

[index or subscript] notice the brackets*

Question 5

an index can be

Answer 5

any integer constant, variable, or expression

Question 6

create an array

Answer 6

someType[] nameOfArray;

Question 7

create an array with specified number of elements

Answer 7

int[] scores = new int [10];

Question 8

what are default values for an array

Answer 8

numeric elements are initialized to 0

boolean to false

Question 9

if array elements are of a class type then…

Answer 9

the array contains references to objects of that type, these are initialized to null

Question 10

if array elements are references, you have to initialize each element by setting it to a valid reference before the element is used

Answer 10

color[0] = new Color (207, 189, 250);
colors[1] = Color.BLUE;

Question 11

what error do you get when you call a method of a non existing object(the reference is null)

Answer 11

nullpointerexception

Question 12

another way to declare and create an array list is to list explicitly like

Answer 12

int [] scores = { 95,97,99, 100 };
String[] names = { “Vika”, “hello”, “justin” };

Color [] rainbowColors =
{
Color.Red, Color.Orange, Color.Grey, Color.Pink
};

Question 13

once an array is declared and initialized, either with the new operator or with a list of values, it is not possible to ?

Answer 13

change its size

Question 14

declare an array of 100 integer elemnts

Answer 14

final int MAXCOUNT = 100;
int[] a = new int [MAXCOUNT];

int[99] is the biggest since index begins at 0

Question 15

how do you find the size of an array

Answer 15

arrayName.length

length acts as a public field that holds the size of an array

In array, length is not a method(as in the String class). It is accessed like a field

Question 16

how are arrays passed to methods?

Answer 16

always as references.
if an array is passed to a method, the method gets the address of the original array and works with the original array, not a copy, therefore a method can change an array passed to it.

Question 17

swap two element’s places in an array

Answer 17

public void swap(double[] a, int i, int j) {
  double temp = a[i];
  a[i] = a[j];
  a[j] = temp;
}

Question 18

declare and initialize a 2-d array of doubles

Answer 18

int rows =2;
int cols =3;

double[] [] a = new doubles [rows] [cols];

double[] []  b =
{
  {0.0, 0.1, 0.2}.
  {1.0, 1.1, 1.2}
};

// each row is an array
// both are two rows and two columns

Question 19

be careful when using break in nested loops, why

Answer 19

a break statement inside a nested loop will only break out of the inner loop

Question 20

define traversal

Answer 20

procedure in which every element of a list is “visited” and processed once. kind of like your order being taken at a mcdonald’s drive thru :P

Question 21

rewrite
String[] names = new String[newGuests];
for (int i = 0; i

Answer 21

for (String str : names) {
  // do something with str
}

or

double sum = 0;
for (double sum : scores) {
sum += num;
}

double average = sum/scores.length;

Question 22

are you able to change the values of an array using an for each loop?

Answer 22

no, you cannot! the variable that refers to an element holds only a copy of the element

for each loop does not give you access to the index of the “visited” element

Question 23

use a for loop to find the largest number of an array

Answer 23

double aMax = 0;

for(int k=0; k aMax ) {
aMax = a[i];
}
}

}