Exercise 4.5

Fermat's Last Theorem says that there are no integers a, b, and c such that

an+bn = cn

except in the case when n = 2.

Write a method named checkFermat that takes four integers as parameters—a, b, c and n—and that checks to see if Fermat’s theorem holds. If n is greater than 2 and it turns out to be true that an+bn = cn, the program should print than 2 and it turns out to be true that an+bn = cn, the program should print 

“Holy smokes, Fermat was wrong!” Otherwise the program should print “No, that doesn’t work.”


You should assume that there is a method named raiseToPow that takes two integers as arguments and that raises the first argument to the power of the second. For example:
     int x = raiseToPow(2,3);
would assign the value 8 to x, because 23 = 8.

Exercise 4.4

QUESTION

What is the output of the following program?

public class Narf {

     public static void zoop(String fred, int bob) {
          System.out.println(fred);
          if (bob == 5 ) {
               ping ("not ");
          } else {
               System.out.println("!");
          }
     }
   
     public static void main(String[] args) {
          int bizz = 5;
          int buzz = 2;
          zoop("just for", bizz);
          clink(2*buzz);
     }

     public static void clink(int fork) {
          System.out.print(It's ");
          zoop("breakfast ", fork) ;
     }

     public static void ping(String strangStrung) {
          System.out.println("any " + strangStrung + "more ");
     }
}

SOLUTION

just for

any not more

It's breakfast

!

Exercise 4.3

QUESTION

The first verse of the song “99 Bottles of Beer” is:

99 bottles of beer on the wall, 99 bottles of beer, ya’ take one down, ya’ pass it around, 98 bottles of beer on the wall.

Subsequent verses are identical except that the number of bottles gets smaller by one in each verse, until the last verse:

No bottles of beer on the wall, no bottles of beer, ya’ can’t take one down, ya’ can’t pass it around, ’cause there are no more bottles of beer on the wall!

And then the song(finally) ends.

Write a program that prints the entire lyrics of “99 Bottles of Beer.” Your program should include a recursive method that does the hard part, but you might want to write additional methods to separate the major functions of the program.

As you develop your code, test it with a small number of verses, like “3 Bottles of Beer.”

The purpose of this exercise is to take a problem and break it into smaller problems, and to solve the smaller problems by writing simple methods.

SOLUTION

public class ThinkJava4_Ex3 {
public static void BeerSong (int beer){
if (beer>0){
System.out.print(beer+" bottles of beer on the wall, ");
System.out.print(beer+" bottles of beer, ya' take one down, ya' pass it around, ");
System.out.println(beer-1+" bottles of beer on the wall.");
BeerSong(beer-1);
} else {
System.out.println("No bottles of beer on the wall, no bottles of beer, ya' can't take one down, ya' can't pass it around, 'cause there are no more bottles of beer on the wall!");
}
}
public static void main (String[]args){
BeerSong (99);
}
}

Exercise 4.2

This exercise reviews the flow of execution through a program with multiple methods. Read the following code and answer the questions below.

public class Buzz {

public static void baffle(String blimp) {

System.out.println(blimp);

zippo("ping", -5);
}

public static void zippo(String quince, int flag) {

if (flag < 0) {

System.out.println(quince + " zoop");
} else {

System.out.println("ik");
baffle(quince);
System.out.println("boo-wa-ha-ha");

}
}

public static void main(String[] args) {

zippo("rattle", 13);
}

}

1. Write the number 1 next to the first statement of this program that will be executed. Be careful to distinguish things that are statements from things that are not.
2. Write the number 2 next to the second statement, and so on until the end of the program. If a statement is executed more than once, it might end up with more than one number next to it.
3. What is the value of the parameter blimp when baffle gets invoked?
4.  What is the output of this program?

SOLUTION

1.

1 System.out.println("ik");

2.

2 System.out.println(blimp);

3 System.out.println(quince + " zoop");

4 System.out.println("boo-wa-ha-ha");

3.Value of parameter blimp when baffle gets invoked is rattle.

4. 

ik

rattle

ping zoop

boo-wa-ha-ha

Exercise 3.4

QUESTION

The purpose of this exercise is to take code from a previous exercise and encapsulate it in a method that takes parameters. You should start with a working solution to Exercise 2.2.

1. Write a method called printAmerican that takes the day, date, month and year as parameters and that prints them in American format.
2. Test your method by invoking it from main and passing appropriate arguments. The output should look something like this (except that the date might be different):

          Saturday, July 16, 2011

      3. Once you have debugged printAmerican, write another method called printEuropean that prints           the date in European format.

SOLUTION

public class ThinkJava3_Ex4 {

//Step 1

public static void printAmerican (String day, int date, String month, int year){

System.out.println(day+", "+month+" "+date+", "+year);

}

//Step 2

public static void main (String []args){

printAmerican("Sat", 2, "Jan", 2016);

//Step 4

printEuropean("Sat", 2, "Jan", 2016);

}

//Step 3

public static void printEuropean (String day, int date, String month, int year){

System.out.println(day+" "+date+" "+month+", "+year);

}

}

Exercise 3.3

QUESTION

The point of this exercise is to make sure you understand how to write and invoke methods that take parameters.

1. Write the first line of a method named zool that takes three parameters: an int and two Strings.
2. Write a line of code that invokes zool, passing as arguments the value 11, the name of your first pet, and the name of the street you grew up on.

SOLUTION

public class ThinkJava3_Ex3 {

//Step 1

public static void zool (int num, String pet, String street){

System.out.println(num);

System.out.println(pet);

System.out.println(street);

}

//Step 2

    public static void main (String[] args){

zool(11, "terrapin", "Woodlands");

}

}

Exercise 3.2

QUESTION

The point of this exercise is to practice reading code and to make sure that you understand the flow of execution through a program with multiple methods.

1. What is the output of the following program? Be precise about where there are spaces and where there are newlines.

          HINT: Start by describing in words that ping and baffle do when they are invoked.

      2. Draw a stack diagram that shows the state of the program the first time ping is invoked.

public static void zoop() {

baffle();

System.out.print("You wugga ");

baffle();
}
public static void main(String[] args) {

System.out.print("No, I ");

zoop();

System.out.print("I ");

baffle();

}
public static void baffle() {

System.out.print("wug");

ping();

}
public static void ping() {

System.out.println(".");

}

SOLUTION

1. 

No, I wug.

You wugga wug.

I wug.