Introduction to Computer Science Unit 5. Programs: Strings

Transcription

1 Introduction to Computer Science Unit 5. Programs: Strings This section must be updated to work with repl.it 1. Copy RunNames and complete the two methods in the Name class. public class Name{ private String first, last; public Name( String s1, String s2 ){ first = s1; last = s2; public class RunNames{ public static void main( String [] args ) { Name n1 = new Name( "Sandy", "Cheeks" ); String s = n1.monogram(); s = n1.reversed(); public String monogram(){ returns the first letters of the two instance variables. public String reversed(){ returns the last name followed by a comma, a space, and the first name Name n2 = new Name( "Pearl", "Krabs" ); s = n2.monogram(); s = n2.reversed(); The above should display: SC Cheeks, Sandy PK Krabs, Pearl 2. Write the tastesgood method in the Soup class then write a second class with a main method. public class Soup { private String i; //ingredients In the main method of some class Create a Soup object. public Soup() { i = "water"; Add onions and then add chicken. Call the tostring method and print. Call the tastesgood method and indicate if it tastes good or not. public void add( String extra ){ i += ", " + extra; public boolean tastesgood(){ Create a second Soup object. Add noodles, rat, and salt (3 method calls) Call tostring and tastes Good as before. The output should look something like this: Page 1

2 Returns false if rat is one of the ingredients; otherwise it returns true. public String tostring() { return "This soup has " + i; 3. Complete the three Student methods and test it with the School class. public class Student { private String name; private String grades; public Student( String n) { name = n; grades = ""; public void add( String g ){ if g's length is not 1, do nothing convert g to an upper case letter add g to grades public int howmany( String g ){ if g has a length that is not 1, return 0 convert g to an upper case letter compare g to every letter in the String grades. Return the number of matches. public String tostring() { String s = name; s += "'s grades are "; s += grades; return s; public class School { public static void main(string[] args) { Student x = new Student( "Emily" ); x.add( "a" ); x.add( "B" ); x.add( "B+" ); x.add( "b" ); x.add( "B" ); x.add( "A" ); System.out.println( x.tostring() ); int n = x.howmany( "a" ); n = x.howmany( "B" ); n = x.howmany( "B+" ); Student y = new Student( "Joe" ); y.add( "c" ); y.add( "a" ); y.add( "C" ); System.out.println( y.tostring() ); n = y.howmany( "b" ); n = y.howmany( "C" ); The output of this program is: Emily's grades are ABBBA Joe's grades are CAC 0 2 Page 2

3 4. This program is a two-player game. The first player enters a word that has at least 3 characters. Then the code instantiates a Jumble object which contains the original word and a scrambled version. The second player only sees the scrambled version and must guess what the original word is. Any text in italics represents code that you must figure out. import java.util.scanner; public class Runner { public static void main(string[] args) { Scanner scan = new Scanner( System.in ); System.out.print("Enter a word "); Jumble jum = new Jumble(scan.nextLine() ); for (int n = 1; n <= 20; n++ ) System.out.println( "Don't look!" ); System.out.println(); String scambled = jum.getjumble(); System.out.println( "The scrambled word is " + scambled ); int num_guesses = 0; String whatisit = ""; while ( ){ In the loop ask the user to enter a guess and increment num_guesses. The user should have to keep guessing until they get it right or they were wrong 5 times. After the loop either print Congratulations if they guessed it or print You lose and whatever the tostring method returns. Here s an example of what should happen. User 1 enters rhythm. Don t look! is printed 20 times.... Don't look! Don't look! public class Jumble { private String secret_word; private String mixedup; public Jumble( String s ) { secret_word = s; Figure out some way to rearrange the letters in s and assign them to mixedup. For example, if s is boat then maybe mixedup would be obta. It would be best if this were done in some random fashion. You may assume that s has at least 3 letters. public String getjumble(){ return mixedup; public boolean guess( String what ){ return true if what equals secret_word otherwise it returns false. public String tostring(){ return mixedup + " is " + secret_word; Page 3

4 The scrambled word is mthryh What is it? thrymh What is it? hrmtyh What is it? myhhrt What is it? trymhh What is it? thymer You lose. mthryh is rhythm User 2 hopelessly guesses 5 times and loses. 5. In this program we will write a simple version of the game Hangman. First, you need to complete the Hangman class. public class Hangman { private String secret; private String display; private int numleft; // this is the actual word // this is what is displayed // this tracks the number of misses left. public Hangman( String s ) { secret = s.touppercase(); numleft = 6; // In our version the player can make up to six mistakes display should contain a series of asterisks equal to the number of characters in secret. Use a loop. public boolean keepplaying() { Returns true if the number of guesses is greater than zero and display does not equal secret. Otherwise return false. public void guess( String guessed_letter ){ guessed_letter = guessed_letter.touppercase(); String newdisplay = ""; for ( int n = 0; n < secret.length(); n++ ){ String actual_letter = secret.substring(n,n+1); String display_letter = display.substring( n, n+1 ); if ( actual_letter.equals( guessed_letter ) ) newdisplay += actual_letter; else newdisplay += display_letter; if something is true then one should be subtracted from numleft display = newdisplay; public boolean won(){ return secret.equals( display ); Page 4

5 public String getsecret(){ return secret; public String tostring() { return display + " You have " + numleft + " guesses left."; Problem 5 continued. Here is an outline of the main method of the second class. Scanner in = new Scanner( System.in ); System.out.print( "Enter a word "); String w = in.nextline(); Hangman h = new Hangman( w ); for (int n = 1; n <= 20; n++ ) System.out.println( "Don't look!" ); System.out.println(); System.out.println( h.tostring() ); System.out.println(); while ( figure this part out ){ Page 5

6 Have the user enter a letter and call the guess method and then call the tostring method If the user won, print Congratulations. If they lost then call the getsecret method so they can see what the word was. To the right is an example of what the finished program should display. Page 6