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 by Chris Thiel, OFMCap */ 
		int i= 0;
		int cnt = 0;
		while ( cnt < n-1 && currentPhrase.indexOf(str, i) >= 0 ) {
			i = currentPhrase.indexOf(str, i) + 1;
			cnt++;
		}
		return currentPhrase.indexOf(str, i);
	}
	
	/** 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) */ 
		return -2019;
	}
	
	/** Returns a string containing the current phrase. */ 
	public String toString()
	{ return currentPhrase; }
	public static void main(String[] args) {
		System.out.println("2017: Phrase Tester\n");
		Phrase p1 = new Phrase( "A cat ate late.");
		System.out.println("Part (a)\n For \""+p1+"\" replaceNthOccurrence\n");
		System.out.println("(\"at\", 1, \"rane\") should return \"A crane ate late.\"");
		p1.replaceNthOccurrence("at", 1, "rane");
		System.out.println("Your code: \"" + p1 +"\"\n");
		p1 = new Phrase( "A cat ate late.");
		Phrase p4 = new Phrase("aaaa");
		System.out.println("(\"at\", 6, \"xx\") should return \"A cat ate late.\"");
		p1 = new Phrase( "A cat ate late.");
		p1.replaceNthOccurrence("at", 6, "xx");
		System.out.println("Your code: \"" + p1 +"\"\n");
		
		System.out.println("(\"bat\", 2, \"xx\") should return \"A cat ate late.\"");
		p1.replaceNthOccurrence("bat", 2, "xx");
		System.out.println("Your code: \"" + p1 +"\"\n");
		
		System.out.println("Part (a)\n For \""+p4+"\" replaceNthOccurrence\n");
		
		System.out.println("(\"aa\", 1, \"xx\") should return \"xxaa\"");
		p4.replaceNthOccurrence("aa", 1, "xx");
		System.out.println("Your code: \"" + p4 +"\"\n");
		
		System.out.println("(\"aa\", 2, \"bbb\") should return \"abbba\"");
		p4 = new Phrase("aaaa");
		p4.replaceNthOccurrence("aa", 2, "bbb");
		System.out.println("Your code: \"" + p4 +"\"\n");
		
		p1 = new Phrase( "A cat ate late.");
		System.out.println("Part (b)\n For \""+p1+"\" findLastOccurrence\n");
		System.out.println("findLastOccurrence(\"at\") should return 11 ");
		
		System.out.println("Your code returns: \"" + p1.findLastOccurrence("at") +"\"\n");
		
		System.out.println("findLastOccurrence(\"cat\") should return 2 ");
		System.out.println("Your code returns: \"" + p1.findLastOccurrence("cat") +"\"\n");
		System.out.println("findLastOccurrence(\"bat\") should return -1 ");
		System.out.println("Your code returns: \"" + p1.findLastOccurrence("bat") +"\"\n");
	}
}