Java Chapter 7

String length vs array length

Array-field: names.length; String-method: name.length();

ArrayList diamond operator

ArrayList<String> list=new ArrayList<>();

ArrayList designate a different capacity

ArrayList<String> list=new ArrayList<String>(100);

creating an ArrayList

ArrayList<String> nameList = new ArrayList<String>();

Which of the following is a correct method header for receiving a two-dimensional array as an argument? A. public static void passArray(int[2]) B. public static void passArray(int [][]) C. public static void passArray(int[1][2]) D. public static void passArray(int[], int[])

B. public static void passArray(int [][])

this is the typical number of comparisons performed by the sequential search on an array of N elements (assuming the search values are consistently found)

N/2

ArrayList toString method

System.out.println(nameList); output: [ James ]

Java does not allow a statement to use a subscript that is outside the range of valid subscripts for an array. T or F

True

volume of a cylinder

V=πr²h

What is the representation of the third element in an array called a?

a[2]

this array field holds the number of elements that the array has

length

2D array length field

length field gives the number of rows each row has a length constant that tells how many columns is in that row

An array's size declarator can be a negative integer expression T or F

false

The first size declarator in the declaration of a two- dimensional array represents the number of columns. The second size declarator represents the number of rows. T or F

false

ArrayList add method

nameList.add("James");

ArrayList modified add method

nameList.add(1, "Mary");

ArrayList get method

nameList.get(1); gets name at index 1

ArrayList remove method

nameList.remove(1);

ArrayList set method

nameList.set(1, "Becky"); replace existing item

ArrayList size method

nameList.size();

A two-dimensional array had multiple length fields T or F

true

An ArrayList automatically expands in size to accommodate the items stored in it. T or F

true

The Java compiler does not display an error message when it processes a statement that uses an invalid subscript T or F

true

The subscript of the last element in a single-dimensional array is one less than the total number of elements in the array T or F

true

both of the following declarations are legal and equivalent: int[] numbers; int numbers[]; T or F

true

the values in an initialization list are stored in the array in the order that they appear in the list T or F

true

when an array is passed to a method, the method has access to the original array T or F

true

array bounds checking happens a. when the program is compiled b. when the program is saved c. when the program runs d. when the program is loaded into memory

when the program runs

ragged array

when the rows of a 2D array are different lengths int[][] ragged=new int [4][]; then create columns: ragged[0]=new int[3]; ragged[1]=new int[4]; etc.

Suppose array a is int[] a = {1, 2, 3}, what is a[0] - a[2]?

-2

Suppose: int[] numbers = new int[10]; What is numbers[0]?

0

the first subscript in an array is always (#)

0

the last subscript in an array is always

1 less than the number of elements

ArrayList default capacity

10

Show the output of the following code: public class Test { public static void main(String[] args) { int[] x = {1, 2, 3, 4, 5}; increase(x); int[] y = {1, 2, 3, 4, 5}; increase(y[0]); System.out.println(x[0] + " " + y[0]);} public static void increase(int[] x) { for (int i = 0; i < x.length; i++) x[i]++;} public static void increase(int y) { y++;}}

2 1

In the following code, what is the printout for list2? class Test { public static void main(String[] args) { int[] list1 = {3, 2, 1}; int[] list2 = {1, 2, 3}; list2 = list1; list1[0] = 0; list1[1] = 1; list2[2] = 2; for (int i = list2.length - 1; i >= 0; i--) System.out.print(list2[i] + " ");}}

2 1 0

If you declare an array double[] list = {3.4, 2.0, 3.5, 5.5}, list[1] is _____

2.0

Surface Area of a Cylinder

2πrh + 2πr^2

What will be the value of x[1] after the following code is executed? int[] x = {22, 33, 44}; arrayProcess(x[1]); ... public static void arrayProcess(int a){ a = a + 5;}

33

What will be the value of x[1] after the following code is executed? int[] x = {22, 33, 44}; arrayProcess(x); ... public static void arrayProcess(int[] a){ for(int k = 0; k < 3; k++){ a[k] = a[k] + 5;}}

38

Assume int[] t = {1, 2, 3, 4}. What is t.length?

4

Assume double[][] x = new double[4][5], what are x.length and x[2].length?

4 and 5

What will be the result of executing the following code? int[] x = {0, 1, 2, 3, 4, 5}; A. An array of 6 values ranging from 0 through 5 and referenced by the variable x will be created. B. A compilation error will occur. C. The program will crash when it is executed. D. The value of x[1] will be 0, x[2] will be 0, x[3] will be 0, x[4] will be 0, x[5] will be 0, and x[6] will be 0.

A. An array of 6 values ranging from 0 through 5 and referenced by the variable x will be created.

What would be the results of the following code? int[] array1 = new int[25]; ... // Code that will put values in array1 int value = array1[0]; for (int a = 1; a < array1.length; a++){ if (array1[a] < value) value = array1[a];} A. value contains the highest value in array1 B. value contains the lowest value in array1 C. value contains the sum of all the values in array1 D. value contains the average of the values in array1

B. value contains the lowest value in array1

For the following code, what would be the value of str[2]? String[] str = {"abc", "def", "ghi", "jkl"}; A. "ghi" B. "def" C. A reference to the String "ghi" D. A reference to the String "def"

C. A reference to the String "ghi"

When you pass an array to a method, the method receives _____. A. a copy of the array B. a copy of the first element C. the reference of the array D. the length of the array

C. the reference of the array

Given the following declaration: nt[ ][ ] m = new int[5][6]; Which of the following statements is true? A. m[2][4] represents the element stored in the 2nd row and the 4th column of m. B. m.length has the value 6. C. m[0].length has the value 5. D. The name m represents a two-dimensional array of 30 int values.

D. The name m represents a two-dimensional array of 30 int values.

When an array is passed to a method _____. A. a reference to the array is passed B. it is passed just as an object C. the method has direct access to the original array D. all of the above

D. all of the above

If numbers is a two-dimensional int array that has been initialized and total is an int that has been set to 0, which of the following will sum all the elements in the array? A. for (int row = 1; row < numbers.length; row++){for (int col = 1; col < numbers.length; col++)total += numbers[row][col];} B. for (int row = 0; row < numbers.length; row++){for (int col = 0; col < numbers.length; col++)total += numbers[row][col];} C. for (int row = 0; row < numbers[row].length; row++){for (int col = 0; col < numbers.length; col++)total += numbers[row][col];} D. for (int row = 0; row < numbers.length; row++){for (int col = 0; col < numbers[row].length; col++)total += numbers[row][col];}

D. for (int row = 0; row < numbers.length; row++){for (int col = 0; col < numbers[row].length; col++)total += numbers[row][col];}

Analyze the following code: public class Test { public static void main(String[] args) { int[] oldList = {1, 2, 3, 4, 5}; reverse(oldList); for (int i = 0; i < oldList.length; i++) System.out.print(oldList[i] + " ");} public static void reverse(int[] list) { int[] newList = new int[list.length]; for (int i = 0; i < list.length; i++) newList[i] = list[list.length - 1 - i]; list = newList;}}

The program displays 1 2 3 4 5.

to insert an item at a specific location in an ArrayList object, you use this method

add

Array List definition and import statement

automatically expands and shrinks import java.util.ArrayList;

This search algorithm repeatedly divides the portion of an array being searched in half.

binary search

When initializing a two-dimensional array, you enclose each row's initialization list in

braces

2D arrays

double[][]scores=new double [3][4]; 1st is rows, second is columns

enhanced for loop

goes through all elements for(datatype elementVariable : array) statement;

String arrays

if an initialization list is not provided then the new keyword must be used to create the array: String[] names=new String[4]; then each element must be initialized: names[0]="Bill"; names[1]="Susan"; etc.

create an array

int[] numbers=new int[6]; //Create an array that holds 6 integers

let user specify array size

int[] tests; Scanner keyboard=new Scanner(System.in); System.out.print("How many tests?"); int numTests=keyboard.nextInt(); tests=new int[numTests];

to delete an item from an ArrayList object, you use this method

remove

binary search

requires the array to be sorted in ascending order, starts in the middle, then will look in the first half or last half of the array depending on the desired value

Access a 2D array element

scores[2][1]=95;

this search algorithm steps through an array, comparing each item with the search value

sequential search

to determine the number of items stored in an ArrayList object, you use this method

size

In an array declaration, this indicates the number of elements that the array will have.

size declarator

selection sort

smallest value is moved to element 0, next smallest to element 1 and so on

Each element of an array is accessed by a number known as a( n) __________.

subscript

Do the following two programs produce the same result? Program I: public class Test { public static void main(String[] args) { int[] list = {1, 2, 3, 4, 5}; reverse(list); for (int i = 0; i < list.length; i++) System.out.print(list[i] + " ");} public static void reverse(int[] list) { int[] newList = new int[list.length]; for (int i = 0; i < list.length; i++) newList[i] = list[list.length - 1 - i]; list = newList;}} Program II: public class Test { public static void main(String[] args) { int[] oldList = {1, 2, 3, 4, 5}; reverse(oldList); for (int i = 0; i < oldList.length; i++) System.out.print(oldList[i] + " ");} public static void reverse(int[] list) { int[] newList = new int[list.length]; for (int i = 0; i < list.length; i++) newList[i] = list[list.length - 1 - i]; list = newList;}}

yes