This question involves analyzing and modifying a string. The following Phrase class maintains a phrase in an instance variable and has methods that access and make changes to the phrase. You will write two methods of the Phrase class.

public class Phrase

{

private String currentPhrase;

/** Constructs a new Phrase object. */

public Phrase(String p)

{ currentPhrase = p; }

/** Returns the index of the nth occurrence of str in the current phrase;

* returns -1 if the nth occurrence does not exist.

* Precondition: str.length() > 0 and n > 0

* Postcondition: the current phrase is not modified.

*/

    public int findNthOccurrence(String str, int n)

{ /* implementation not shown */ }

/** Modifies the current phrase by replacing the nth occurrence of str with repl.

* If the nth occurrence does not exist, the current phrase is unchanged.

* Precondition: str.length() > 0 and n > 0

*/

    public void replaceNthOccurrence(String str, int n, String repl)

{ /* to be implemented in part (a) */ }

/** Returns the index of the last occurrence of str in the current phrase;

* returns -1 if str is not found.

* Precondition: str.length() > 0

* Postcondition: the current phrase is not modified.

*/

    public int findLastOccurrence(String str)

{ /* to be implemented in part (b) */ }

/** Returns a string containing the current phrase. */

public String toString()

{ return currentPhrase; }

}

Part A

Write the Phrase method replaceNthOccurrence, which will replace the nth occurrence of the string str with the string repl. If the nth occurrence does not exist, currentPhrase remains unchanged.

Several examples of the behavior of the method replaceNthOccurrence are shown below.

Class information for this question

public class Phrase

private String currentPhrase

public Phrase(String p)

public int findNthOccurrence(String str, int n)

public void replaceNthOccurrence(String str, int n, String repl)

public int findLastOccurrence(String str)

public String toString()

The Phrase class includes the method findNthOccurrence, which returns the nth occurrence of a given string. You must use findNthOccurrence appropriately to receive full credit.

Complete method replaceNthOccurrence.