Transcript int[] anArray = new int[10]

CiS 260: App Dev I
Introduction to Arrays
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An array is an object that contains a collection
of components (_________) of the same data
type.
For a one-dimensional array, the collection is a
simple ______.
To declare a one-dimensional array
 int[] anArray; // reference variable declared
 int anArray []; // does the same thing
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To then __________ this one-dimensional array
with 10 elements
 anArray = new int[10]; // elements declared
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You can do both in one statement
 int[] anArray = new int[10]; or
 int j = 10; int[] anArray = new int[j];
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Accessing Array Components
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An array component has the form anArray[i]
where i ranges from __ to anArray.length - 1.
[] is the array subscripting __________.
anArray[0] is the first element in the array and
can be treated like any other __________.
anArray[0] = 5; assigns 5 to anArray[0].
The following statements also assign a value to
an array element
 int i = 7;
 anArray[i] = 42;
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The following declares, instantiates, and loads
 double [] myArray = {5.0, 10.0, 15.0, 20.0};
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Example on p. 479
import java.io.*;
for(counter = 0; counter < 5; counter++)
{
item[counter] =
Integer.parseInt(keyboard.readLine());
sum = sum + item[counter];
}
public class ReversePrintII
{
static BufferedReader keyboard =
new BufferedReader(new
InputStreamReader(System.in));
System.out.println("The sum of the
numbers = " + sum);
System.out.print("The numbers in the
reverse order are: ");
public static void main (String[] args)
throws IOException
{
int[] item = new int[5];
int sum, int counter;
for(counter = 4; counter >= 0; counter--)
System.out.print(item[counter] + " ");
System.out.println("Enter five integers,
one " + "integer per line");
System.out.println();
}
sum = 0;
}
Arrays as Parameters to Methods
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An array is an _______ and can be passed as
an argument to a method.
Example
public static void main(String [] args){
double [] myArray = {5.0, 10.0, 15.0, 20.0};
printArray(myArray);
}
public static void printArray(double[] anArray){
for(int i = 0; i < anArray.length; i++)
System.out.println(anArray[i]);
}
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The _____ address of an array is the address of
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the first array component, such as myArray[0].
Parallel Arrays
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Two or more arrays are parallel if their
corresponding components (__________) hold
related information.
Example
 int [] studentID = new int[50];
 double [] totalScore = new double[50];
 char [] courseGrade = new char[50];
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Thus, studentID(22), totalScore(22), and
courseGrade(___) would all refer to the same
student.
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Arrays of Objects
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Arrays can hold __________ such as int’s,
double’s and char’s.
In Java, arrays can also hold _______ which in
turn can hold data of differing types (such as
primitives or other objects).
Suppose you have employees and each
employee has an arrival and a departure time.
You can create arrays for employees, their
arrival times, and their departure times:
 Employee[] companyEmp = new Employee[100];
 Clock[] arrivalTimeEmp = new Clock[100];
 Clock[] departureTimeEmp = new Clock[100];
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Two-Dimensional Arrays
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A one-dimensional array is used for data in list
form (e.g., a list of names or a list of scores).
A two-dimensional array is used for data in ____
form where all data have the same _____.
Characteristics of tables are rows and _______.
The general syntax is
 dataType[][] arrayName = new dataType[#rows][#cols];
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Example of sales by month (0-11) for five car
makers (Chrysler, GM, Ford, Honda, Toyota):
 double[][] sales = new double[12][5];
 sales[5][3] = 25.75; // store in row 5, col 3
 sales[7] is the sales array for all cars in _______
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Ragged Two-Dimensional Arrays
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A ragged two-dim array has uneven _______.
int [][] raggedArray = new int [3]; // # of rows
raggedArray[0] = new int[4]; // # cols in 1st row
raggedArray[1] = new int[1];
raggedArray[2] = new int[2];
raggedArray[0][0] = 6;
raggedArray[0][1] = 17;
…
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Load a two-dim array at declaration
 int [][] raggedArray = {{6,17,5,2},{14},{-2,8}};
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Load a two-dim array using ________ loops
for(int i = 0; i < raggedArray.length; i++)
for(int j = 0; j < raggedArray[j].length; j++)
raggedArray[i][j] = i;
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Multidimensional Arrays
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Multi-dim arrays just extend two-dim arrays.
Load random numbers in a 3-dim array
double [][][] randomNums = new double [5][5][5];
for(int i=0; i<randomNums.length; i++)
for(int j=0; j<randomNums[i][j].length; j++)
for(int k=0; k<randomNums[i][j][k].length; k++)
randomNums[i][j][k] = Math.random();
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Add the random numbers in the array
double sum = 0;
for(int i=0; i<randomNums.length; i++)
for(int j=0; j<randomNums[i][j].length; j++)
for(int k=0; k<randomNums[i][j][k].length; k++)
sum += randomNums[i][j][k];
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