2D Arrays Review

Examine the following:

double[][] values =

{ {1.2, 9.0, 3.2},

{9.2, 0.5, -1.2},

{7.3, 7.9, 4.8} } ;

what is in values[2][1] ?

• 7.9

• 9.2

• 7.3

• 0.5

Given the following:

double[][] things =

{ {1.2, 9.0, 8.7, 1.0},

{9.2, 0.5, 0.0, 5.2},

{7.3, 7.9, 1.2, 3.9} } ;

What is the value of things.length ?

• 4

• 3

• 12

• 7

Given the following:

long [][] stuff ;

Which of the following statements constructs an array with 5 rows of 7 columns each and assign its reference to stuff ?

• stuff = new stuff[5][7] ;

• stuff = new long[5][7] ;

• stuff = long[5][7] ;

• stuff = long[7][5] ;

Given:

int[][] items =

{ {0, 1, 3, 4},

{4, 3, 99, 0},

{3, 2, 7, 70} } ;

Which of the following fragments prints out every element of items?

• for ( int row=0; row < items.length; row++ )

  {

  System.out.println();

  for ( int col=0; col < items.length; col++ )

  System.out.print( items[row][col] + " ");

  }

• for ( int row=0; row < items.length; row++ )

  {

  System.out.println();

  for ( int col=0; col < items[col].length; col++ )

  System.out.print( items[row][col] + " ");

  }

• for ( int row=0; row < items.length; row++ )

  {

  for ( int row=0; row < items[row].length; row++ )

  System.out.print( items[row][col] + " ");

  System.out.println();

  }

• for ( int row=0; row < items.length; row++ )

  {

  System.out.println();

  for ( int col=0; col < items[row].length; col++ )

  System.out.print( items[row][col] + " ");

  }

Each piece of data in an array is BEST described as a what?

• Integer and string

• Item

• Element

• Elephant

Which BEST describes an array?

• A data structure - Stores a collection of values under one name

• A data collection - Stores a list of variables

• A list - Stores a list of numbers

• A list - Stores a list of strings

Each element in an array can be accessed using its what?

• By counting in the items in the array

• Position or index in the array

• By printing the items in the array

• By printing and counting the entire array

Why are arrays useful?

• It saves storage space storing under one name

• You can store integers and strings together

• You can store thing related on different topics

• You may have lots of related data that you don't want to store separately

Which of the following statements correctly declares a two-dimensional integer array?

• int matrix[ ] = new int[5,4];

• int matrix[ ]; matrix = new int[5,4];

• int matrix[ ][ ] = new int[5][4];

• int matrix[ ][ ] = int[5][4];

How would you get the value 6 out of the following 2D array int[][] a = {{2, 4, 6, 8}, {1, 2, 3, 4}};?

• a [0][3]

• a [1][3]

• c) a[0][2]

• d) a[2][0]

• e) a[3][1]