Chapter 9 - Fill In The Code

Question 1

For Questions 33 to 37, consider the following statement:

String [ ][ ] geo = { { “MD”, “NY”, “NJ”, “MA”, “ME”, “CA”, “MI”, “OR” },{ “Detroit”, “Newark”, “Boston”, “Seattle” } };

33. This code prints the element at row index 1 and column index 2 of the two-dimensional array geo.

// your code goes here

Answer 1

System.out.println( geo[1][2] );

Question 2

For Questions 33 to 37, consider the following statement:

String [ ][ ] geo = { { “MD”, “NY”, “NJ”, “MA”, “ME”, “CA”, “MI”, “OR” },{ “Detroit”, “Newark”, “Boston”, “Seattle” } };

34. This code prints the element of the array geo whose value is “CA.”

// your code goes here

Answer 2

System.out.println( geo[0][5] );

Question 3

For Questions 33 to 37, consider the following statement:

String [ ][ ] geo = { { “MD”, “NY”, “NJ”, “MA”, “ME”, “CA”, “MI”, “OR” },{ “Detroit”, “Newark”, “Boston”, “Seattle” } };

35. This code prints all the states (i.e., the first row) that start with an M in the array geo.

for ( int j = 0; j < geo[0].length; j++ )
{
       // your code goes here
}

Answer 3

for ( int j = 0; j < geo[0].length; j++ )
{
if ( geo[0][j].charAt( 0 ) == 'M' )
 System.out.println( geo[0][j] );
}

Question 4

For Questions 33 to 37, consider the following statement:

String [ ][ ] geo = { { “MD”, “NY”, “NJ”, “MA”, “ME”, “CA”, “MI”, “OR” },{ “Detroit”, “Newark”, “Boston”, “Seattle” } };

36. This code prints all the cities (i.e., the second row) in the array geo.

for ( int j = 0; j < geo[1].length; j++ )
{
       // your code goes here
}

Answer 4

for ( int j = 0; j < geo[1].length; j++ )
{
System.out.println( geo[1][j] );
}

Question 5

For Questions 33 to 37, consider the following statement:

String [ ][ ] geo = { { “MD”, “NY”, “NJ”, “MA”, “ME”, “CA”, “MI”, “OR” },{ “Detroit”, “Newark”, “Boston”, “Seattle” } };

37. This code prints all the elements of the array geo.

for ( int i = 0; i < geo.length; i++ )
{
      // your code goes here
}

Answer 5

for ( int i = 0; i < geo.length; i++ )
{
for ( int j = 0; j < geo[i].length; j++ )
System.out.println( geo[i][j] );
}

Question 6

For Questions 38 to 41, consider the following statement:

int [ ][ ] a = { { 9, 6, 8, 10, 5 },
{ 7, 6, 8, 9, 6 },
{ 4, 8, 10, 6, 6 } };

38. This code calculates and prints the sum of all the elements in the array a.

int sum = 0;
for ( int i = 0; i < a.length; i++ )
{
      // your code goes here
}
System.out.println( "sum is " + sum );

Answer 6

int sum = 0;
for ( int i = 0; i < a.length; i++ )
{
for ( int j = 0; j < a[i].length; j++ )
sum += a[i][j];
}
System.out.println( "The sum is " + sum );

Question 7

For Questions 38 to 41, consider the following statement:

int [ ][ ] a = { { 9, 6, 8, 10, 5 },
{ 7, 6, 8, 9, 6 },
{ 4, 8, 10, 6, 6 } };

39. This code counts and prints the number of times the value 8 appears in the array a.

int count = 0;
for ( int i = 0; i < a.length; i++ )
{
      // your code goes here
}
System.out.println( "# of 8s in a: " + count );

Answer 7

int count = 0;
for ( int i = 0; i < a.length; i++ )
{
for ( int j = 0; j < a[i].length; j++ )
{
 if ( a[i][j] == 8 )
count++;
}
}
System.out.println( "# of 8s in a: " + count );

Question 8

For Questions 38 to 41, consider the following statement:

int [ ][ ] a = { { 9, 6, 8, 10, 5 },
{ 7, 6, 8, 9, 6 },
{ 4, 8, 10, 6, 6 } };

40. This code counts and prints the number of times the value 6 appears in the second row (i.e., the row whose index is 1) of array a.

int count = 0;

// your code for the for loop header goes here
{
if ( a[1][j] == 6 )
count++;
}
System.out.println( “# of 6s in the 2nd row: “ + count );

Answer 8

int count = 0;
for ( int j = 0; j < a[1].length; j++ )
{
 if ( a[1][j] == 6 )
 count++;
}
System.out.println( "# of 6s in the 2nd row: " + count );

Question 9

For Questions 38 to 41, consider the following statement:

int [ ][ ] a = { { 9, 6, 8, 10, 5 },
{ 7, 6, 8, 9, 6 },
{ 4, 8, 10, 6, 6 } };

41. This code calculates the sum of the elements in the second column (i.e, the column with index 1) of array a.

int sum  = 0;
for ( int i = 0; i < a.length; i++ )
{
   // your code goes here

}
System.out.println( “sum is “ + sum );

Answer 9

int sum = 0;
for ( int i = 0; i < a.length; i++ )
{
if ( a[i].length >= 2 )
sum += a[i][1];
}
System.out.println( "sum is " + sum );

Question 10

42. This method returns true if an element in an array of Strings is equal to “Java”; otherwise, it returns false.

public static boolean foo( String [ ][ ] a )
{
   // your code goes here
}

Answer 10

public static boolean foo( String [][] a )
{
for( int i = 0; i < a.length; i++ )
{
 for ( int j = 0; j < a[i].length; j++ )
 {
 if ( a[i][j].equals( "Java" ) )
return true;
 }
}
return false;
}

Question 11

43. This method returns the product of all the elements in an array.

public static int foo( int [ ][ ] a )
{
   // your code goes here
}

Answer 11

public static int foo( int [][] a )
{
int product = 1;
for ( int i = 0; i < a.length; i++ )
{
 for ( int j = 0; j < a[i].length; j++ )
 {
 product *= a[i][j];
 }
}
return product;
}

Question 12

44. This method returns true if there is at least one row in the array that has exactly five columns; otherwise, it returns false.

public static boolean foo( char [ ][ ] a )
{
   // your code goes here
}

Answer 12

public static boolean foo( char [][] a )
{
for ( int i = 0; i < a.length; i++ )
{
 if ( a[i].length == 5 )
return true;
}
return false;
}

Question 13

45. This method takes an array of ints as a parameter and returns a single-dimensional array of booleans. The length of the array returned should be equal to the number of rows in the two-dimensional array parameter. The element at index i of the returned array will be true if there is a 0 in the corresponding row of the parameter array; otherwise, it will be false. Assume that every row in a has the same number of columns.

public static boolean [ ] foo( int [ ][ ] a )
{
   // your code goes here
   // every row has the same number of columns
}

Answer 13

public static boolean [] foo( int [][] a )
{
boolean [] temp = new boolean[a.length];
for ( int i = 0; i < a.length; i++ )
{
 for ( int j = 0; j < a[i].length; j++ )
 {
 if ( a[i][j] == 0 )
temp[i] = true;
 }
}
return temp;
}

Question 14

For Questions 46 to 49, consider the following statements:

ArrayList languages = new ArrayList( );

languages. add( “SQL” );
languages. add( “Java” );
languages. add( “HTML” );
languages. add( “PHP” );
languages. add( “Perl” );

46. This code prints the number of elements in languages.

// your code goes here

Answer 14

System.out.println( languages.size( ) );

Question 15

For Questions 46 to 49, consider the following statements:

ArrayList languages = new ArrayList( );

languages. add( “SQL” );
languages. add( “Java” );
languages. add( “HTML” );
languages. add( “PHP” );
languages. add( “Perl” );

47. This code retrieves the String “HTML” from languages (without deleting it) and assigns it to the String variable webLanguage.

// your code goes here

Answer 15

String webLanguage = languages.get( 2 );

Question 16

For Questions 46 to 49, consider the following statements:

ArrayList languages = new ArrayList( );

languages. add( “SQL” );
languages. add( “Java” );
languages. add( “HTML” );
languages. add( “PHP” );
languages. add( “Perl” );

48. This code replaces “HTML” with “C++” in languages.

// your code goes here

Answer 16

languages.set( 2, “C++” );

Question 17

For Questions 46 to 49, consider the following statements:

ArrayList languages = new ArrayList( );

languages. add( “SQL” );
languages. add( “Java” );
languages. add( “HTML” );
languages. add( “PHP” );
languages. add( “Perl” );

49. This code prints all the elements of languages that start with the letter P.

for ( String s : languages )
{  
  // your code goes here
}

Answer 17

for ( String s : languages )
{
if ( s.charAt( 0 ) == 'P' )
 System.out.println( s );
}