Reference types - Data Structures and Problem Solving Using Java - page 65

Implement the following method that returns the index of the row that
contains the most zeros.

2.18

public static int rowWithMostZeros( int [ ] [ ] arr )

Implement the various hasDuplicates methods, which all return true if
there are any duplicate entries in the specified group of elements.

2.19

public static boolean hasDuplicates( int [ ] arr )
public static boolean hasDuplicates( int [ ][ ] arr )
public static boolean hasDuplicates( String [ ] arr )
public static boolean hasDuplicates( ArrayList<String> arr )

Implement both howMany methods, which return the number of occur-
rences of val in arr .

2.20

public static int howMany( int [ ] arr, int val )
public static int howMany( int [ ][ ] arr, int val )

Implement both countChars methods, which return the number of
occurrences of ch in str .

2.21

public static int countChars( String str, char ch )
public static int countChars( String [ ] str, char ch )

Using the String method toLowerCase , which creates a new String that is
the lower case equivalent of an existing String (i.e., str.toLowerCase

2.22

()
returns a lower case equivalent of str , while leaving str unchanged), imple-
ment the getLowerCase and makeLowerCase methods below. getLowerCase
returns a new collection of String s, while makeLowerCase modifies the
existing collection.

public static String [ ] getLowerCase( String [ ] arr )
public static void makeLowerCase( String [ ] arr )
public static ArrayList<String> getLowerCase( ArrayList<String> arr )
public static void makeLowerCase( ArrayList<String> arr )

Method isIncreasing returns true if in each row of the two-dimensional
array, all entries monotonically increase, and in each column all entries
also monotonically increase. Implement isIncreasing .

2.23

public static boolean isIncreasing( int [ ] [ ] arr )

Implement method startsWith which returns an ArrayList containing
all the String sin arr that begin with character ch .

2.24

public ArrayList<String> startsWith( String [ ] arr, char ch )