LAB 2. Objective: Navin Sridhar D 8 54

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1 LAB 2 Objective: 1. Understand the classes, methods (library and userdefined), datatypes and type conversion in Java. 2. Learn to use parameters & pass multiple arguments and draw stack diagrams. 3. Learn to use conditionals and recursion techniques for writing complex programs. Navin Sridhar D 8 54

2 Chapter 3 Exercises Exercise 3.1. Q. Draw a stack frame. main printtime hour 11 printtime minute 59 Exercise 3.2. Q. Understanding the flow of execution of a program. - What is the output of the following program? public static void zoop() { baffle(); System.out.print("You wugga "); baffle(); 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("."); - ping and baffle are two methods defined separately. - When ping is invoked, a period (.) is printed with a newline added after it. - baffle prints a statement wug, and then calls the method ping (which prints a period and adds a newline).

3 Flow of execution: 1) main zoop baffle ping zoop baffle ping "No, I " "wug" "." "You wugga " "wug" "." 2) main baffle ping OUTPUT: "I " "wug" "." STACK DIAGRAM: main No, I zoop baffle wug ping. Exercise 3.3. Q. Write the first line of a method named zool that takes three parameters: an int and two Strings. 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. - public static void zool(int i, String s1, String s2) { zool(11, "tiny", "pestom sagar");

4 Exercise 3.4. Q. Write two methods called printamerican and printeuropean that takes the day, date, month and year as parameters and that prints them in American and European formats. - class AMERICANDateusingmethod { OUTPUT: // JAVA Program to display a date in the American Format. // Navin Sridhar public static void printamerican(string day, int date, String month, int year) { System.out.println(day + ", " + month + " " + date + ", " + year); printamerican("saturday", 16, "July", 2011); - class EUROPEANDateusingmethod { OUTPUT: // JAVA Program to display a date in the European Format. // Navin Sridhar public static void printeuropean(string day, int date, String month, int year) { System.out.println(day + " " + date + " " + month + ", " + year); printeuropean("saturday", 16, "July", 2011);

5 Chapter 4 Exercises Exercise 4.1. Q. Draw a stack diagram that shows the state of the program after main invokes nlines with the parameter n=4, just before the last invocation of nlines returns. main nlines nlines nlines nlines nlines n 4 n 3 n 2 n 1 n 0 Exercise 4.2. Q. 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"); zippo("rattle", 13); - Write numbers beside the lines of the code given above which indicate their order of execution.

6 Order of execution public class Buzz { public static void baffle(string blimp) { System.out.println(blimp); 5 zippo("ping", -5); 6 public static void zippo(string quince, int flag) { if (flag < 0) { 2, 7 System.out.println(quince + " zoop"); 8 else { System.out.println("ik"); 3 baffle(quince); 4 System.out.println("boo-wa-ha-ha"); 9 zippo("rattle", 13); 1 Q. What is the value of the parameter blimp when baffle gets invoked? - When baffle gets invoked, value of the parameter blimp is rattle. Q. What is the output of this program? - The output of this program is as shown in the picture below:

7 Exercise 4.3. Q. Write a program that prints the entire lyrics of 99 Bottles of Beer. - class bottlesofbeer { // JAVA Program to display the lyrics of "99 Bottles of Beer" using recursion technique. // Navin Sridhar nbottles(99); public static void nbottles(int n) { if (n == 0) { lastbottle(); else if (n == 2) { System.out.println("2 bottles of beer on the wall, 2 bottles of beer, ya\u0027 take one down, ya\u0027 pass it around, one more bottle of beer on the wall."); nbottles(n-1); else if (n == 1) { System.out.println("One bottle of beer on the wall, one bottle of beer, ya\u0027 take one down, ya\u0027 pass it around, no more bottles of beer on the wall."); nbottles(n-1); else { System.out.println(n + " bottles of beer on the wall, " + n + " bottles of beer, ya\u0027 take one down, ya\u0027 pass it around, " + (n-1) + " bottles of beer on the wall."); nbottles(n-1); public static void lastbottle() { System.out.println("No bottles of beer on the wall, no bottles of beer, ya\u0027 can\u0027t take one down, ya\u0027 can\u0027t pass it around, \u0027cause there are no more bottles of beer on the wall!");

8 Exercise 4.4. Q. 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("!"); 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 "); OUTPUT: Execution always begins at the first statement of main. main 1) bizz = 5, buzz = 2 2) It invokes zoop, passing a string just for and bizz (i.e. 5) as arguments. zoop 1) just for is printed. 2) As bob (which was bizz in main) is equal to 5, 3) ping is invoked passing a string not as an argument. ping 1) any not more is printed. 2) It returns to zoop. zoop returns to main. main 1) It invokes clink, passing 2*buzz (where buzz=2) as an argument. clink 1) It s is printed. 2) It invokes zoop, passing a string breakfast and fork (whose value is 2*buzz = 4) as arguments. zoop 1) breakfast is printed. 2) As bob (which was fork in clink) is not equal to 5, 3)! is printed. 4) It returns to clink clink returns to main. END OF EXECUTION.

9 Exercise 4.5. Q. Fermat s Last Theorem says that there are no integers a, b, and c such that 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. - class FermatsLastTheorem { // In this program, values taken are a = 3, b = 4, c = 5, n = 3. // x = a raised to n using the raisetopow method. // y = b raised to n using the raisetopow method. // z = c raised to n using the raisetopow method. // Math.pow gives answer in double. So datatype of x, y, z is double. // checkfermat method checks for the necessary conditions. // Navin Sridhar public static void checkfermat(double u, double v, double w, int n) { if ((n>2)&&((u + v) == w)) { System.out.println("Holy smokes, Fermat was wrong!"); else { System.out.println("No, that doesn\u0027t work."); int a = 3, b = 4, c = 5, n = 3; double x = raisetopow(a,n); double y = raisetopow(b,n); double z = raisetopow(c,n); checkfermat(x, y, z, n); public static double raisetopow(int r, int s) { return Math.pow(r, s);

10 CONCLUSION i) Programs with multiple methods: Solutions to five programs were based on a simple rule - Execution always begins at the first statement of main. The main then invokes any other method passing or not passing arguments to it. Most of the times, main is the parent method and all other methods are it s child. While reading a program, always follow the flow of execution and refer to Stack Diagrams. ii) iii) iv) Basic rules for methods and classes: - You can invoke the same procedure more than once. A method may invoke itself (which would be known as recursion) or invoke other methods. - Spaces and new lines usually don t change the meaning of a program. It is usually a good idea to put each statement on its own line to avoid confusion. - If a method defined in some other class is to be used in the current class, the method name should be preceded by the classname and a period (Ex.: CLASS.method). - classes which are defined as public should be declared in a file with the same filename as the classname. Using the return statement: The return statement may be used to terminate the execution either by returning a value or not. Methods may be written either to return a value or to perform some pre-defined function. For the return statement to return a value, the appropriate return type should be specified in the method definition else the compiler will report an error. Conditional statements: To write useful programs, we almost always need to check conditions and change the behavior of the program accordingly. If the condition in the parentheses is true, then the statements following it get executed. If the condition is not true, nothing happens. This feature helps us in creating error messages and helps the program send accurate output depending on the user s different inputs by checking conditions.