1. Methods (Functions)
CSE 1310 – Introduction to Computers and Programming
Alexandra Stefan and Vassilis Athitsos
University of Texas at Arlington

2. What Is a Method?
A method is a mechanism for allowing a piece of code to be executed more than once, in a safe way.
Examples of method usage:
s.length(), s.indexOf(s2), Math.floor(3.4)…
Syntax
Communication with the calling line.
Signature of the method
Parameters
Return value (when appropriate)

3. What Is a Method A method is a piece of code that does a specific job.
Usually the job is to compute and return something. Examples:
Seen: s.length(), s.indexOf(s2), s.charAt(i), Math.floor(n),
Computing the square of a number.
Determining if an number is prime.
Computing the number of digits of a number.
Counting the number of vowels in a string.
Some functions will not return anything. Examples:
Seen: System.out.printf(….),
Print: a banner, a table, a menu
Change/interact with the file system
Write in a file.

4. Terminology: Methods/Functions
In Java, the term methods is the one mainly used.
In some other languages, the term functions is more common.
In some languages (e.g., C++) methods and functions have minor differences in meaning.
In this course, I will use the two terms (methods and functions) as synonyms.
New terms:
Function/method
Function call,
Caller function (caller) vs function being called (callee)
Arguments/parameters
Return, return value, ‘what does the function return?’
Method signature

5. Example import java.util.Scanner; public class example1 {
public static double square(double number) {
double result = number * number;
return result; }
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);

6. A First Example Here we see our first example of a function.
It is called square.
Its job is to compute the square of a number.
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);

7. How to Write a Function Specify a name, like square. function name
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);
function name

8. How to Write a Function Specify a name, like square.
Specify the inputs (called parameters).
The parameters are the input that the function needs in order to compute an output.
For example, what does the square function take as input?
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);

9. How to Write a Function Specify a name, like square.
Specify the inputs (called parameters).
The parameters are the input that the function needs in order to compute an output.
For example, what does the square function take as input?
A number.
We can have functions with 0, 1, or more arguments. We will see examples later.
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);
parameter(s)

10. How to Write a Function Specify a name, like square.
Specify the inputs (called parameters).
Specify the return type of the function.
What is the type of the value that the function computes?
In other words, what values are legal and illegal for the output of the function?
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);
return type

11. How to Write a Function Specify a name, like square.
Specify the inputs (called parameters).
Specify the return type of the function.
Specify what the function does. This is what we call the body of the function.
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);
body

12. How to Write a Function Specify a name, like square.
Specify the inputs (called parameters).
Specify the return type of the function.
Specify what the function does. This is what we call the body of the function.
Specify what value the function returns, using one or more return statements.
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);
return statement

13. Using a Function (Function Calls)
Once you have written a function, you can use it anywhere in your code, by doing a function call.
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);
function call

14. Using a Function (Function Calls)
Once you have written a function, you can use it anywhere in your code, by doing a function call.
When you call a function, you must:
Provide the appropriate argument(s).
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);
argument(s)

15. Using a Function (Function Calls)
Once you have written a function, you can use it anywhere in your code, by doing a function call.
When you call a function, you must:
Provide the appropriate argument(s).
Use the return value appropriately.
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);
storing the return value

16. Using the Return Value
In the square function, the return value is a double.
You can use this value in any way that you can use any double number. Examples:
You can store the return value in a variable.
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);
storing the return value in a variable

17. Using the Return Value
In the square function, the return value is a double.
You can use this value in any way that you can use any double number. Examples:
You can store the return value in a variable.
You can print the return value directly.
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
System.out.printf("%.2f squared = %.2f\n", N, square(N));
printing the return value directly

18. Using the Return Value
In the square function, the return value is a double.
You can use this value in any way that you can use any double number. Examples:
You can store the return value in a variable.
You can print the return value directly.
You can use it as part of a more complicated expression.
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double my_var = 18 + square(N);
System.out.printf("result = %.2f\n", my_var);
using the return value in an expression

19. Using the Return Value
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number: ");
double N = in.nextDouble();
double my_var = 18 + square(square(N));
System.out.printf("result = %.2f\n", my_var);
In the square function, the return value is a double.
You can use this value in any way that you can use any double number. Examples:
You can store the return value in a variable.
You can print the return value directly.
You can use it as part of a more complicated expression.
You can use it as an argument for another function call.
the return value is used as argument for another function call

20. Function Calls You can call a function as many times as you like.
On the next slide, we call the square function three times.

21. Example: Calling the square function many times.
import java.util.Scanner;
public class example1 {
public static double square(double number)
double result = number * number;
return result; }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Please enter a number M: ");
double M = in.nextDouble();
System.out.printf("Please enter a number N: ");
double N = in.nextDouble();
double M_square = square(M);
System.out.printf("%.2f squared = %.2f\n", M, M_square);
double N_square = square(N);
System.out.printf("%.2f squared = %.2f\n", N, N_square);
double MN_square = square(M*N);
System.out.printf("%.2f squared = %.2f\n", M*N, M*N_square);
System.out.printf("%.2f squared = %.2f\n", N, square(N) );
System.out.printf("%.2f to the 4th= %.2f\n", N, square(square(N)) );
Example: Calling the square function many times.

22. Example: Printing Prime Numbers
Write a program that:
Asks the user to enter an integer N.
Prints all prime integers from 2 up to (and including) N.
Identify the solution components
………………….

23. Example: Printing Prime Numbers
Write a program that:
Asks the user to enter an integer N.
Prints all prime integers from 2 up to (and including) N.
Identify the solution components
Read N from user.
Generate ints 2 to N.
Print numbers that satisfy a certain property.
Try with an easier property: even
Check if a single int is prime.

24. Example: Printing Prime Numbers
Write a program that:
Asks the user to enter an integer N.
Prints all prime integers from 2 up to (and including) N.
First step:
Write the basic structure of the program. (steps 1-3)
Put placeholders where more detail is needed.
import java.util.Scanner;
public class example1 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Enter an integer: ");
int N = in.nextInt();
for (int i = 2; i <= N; i++) {
if i is prime
System.out.printf("%d\n", i); }

25. Example: Printing Prime Numbers
Write a program that:
Asks the user to enter an integer N.
Prints all prime integers from 2 up to (and including) N.
Second step:
Identify functions that can be used to complete the program.
import java.util.Scanner;
public class example1 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Enter an integer: ");
int N = in.nextInt();
for (int i = 2; i <= N; i++) {
if i is prime
System.out.printf("%d\n", i); }

26. Example: Printing Prime Numbers
Write a program that:
Asks the user to enter an integer N.
Prints all prime integers from 2 up to (and including) N.
We can use a function is_prime to check if i is prime.
Arguments?
Return type?
import java.util.Scanner;
public class example1 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Enter an integer: ");
int N = in.nextInt();
for (int i = 2; i <= N; i++) {
if i is prime
System.out.printf("%d\n", i); }

27. Example: Printing Prime Numbers
Write a program that:
Asks the user to enter an integer N.
Prints all prime integers from 2 up to (and including) N.
We can use a function is_prime to check if i is prime.
Arguments? an integer
Return type? boolean
import java.util.Scanner;
public class example1 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Enter an integer: ");
int N = in.nextInt();
for (int i = 2; i <= N; i++) {
if i is prime
System.out.printf("%d\n", i); }

28. Example: Printing Prime Numbers
Write a program that:
Asks the user to enter an integer N.
Prints all prime integers from 2 up to (and including) N.
Step 3: use the function.
We have not written the function yet, but that is OK.
Obviously, the program will not run until we write the function.
import java.util.Scanner;
public class example1 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Enter an integer: ");
int N = in.nextInt();
for (int i = 2; i <= N; i++) {
if (is_prime(i))
System.out.printf("%d\n", i); }

29. Step 4: write the function.
import java.util.Scanner;
public class example1 {
public static boolean is_prime(int N) {
for (int i = 2; i < N; i++)
if (N % i == 0)
return false; }
return true;
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Enter an integer: ");
int N = in.nextInt();
for (int i = 2; i <= N; i++)
if (is_prime(i))
System.out.printf("%d\n", i);
}}}}
Write a program that:
Asks the user to enter an integer N.
Prints all prime integers from 2 up to (and including) N.
Step 4: write the function.

30. Output: import java.util.Scanner; public class example1 {
Enter an integer: 80 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79
import java.util.Scanner;
public class example1 {
public static boolean is_prime(int N) {
for (int i = 2; i < N; i++)
if (N % i == 0)
return false; }
return true;
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Enter an integer: ");
int N = in.nextInt();
for (int i = 2; i <= N; i++)
if (is_prime(i))
System.out.printf("%d\n", i);
}}}}

31. Why Do We Need Functions
To write better code:
More correct, easier to read/write/change.
To write complicated code.
Like we did in the example above: we could focus on different aspects without entangling the code :
generating the numbers,
checking if prime or not.
Functions ‘reduce’ the complexity of your code. E.g. using a function, a nested loop could become a single loop (and the code for the inner loop will be in the function).
Functions help us organize code and share code.
YOU CANNOT WRITE NON-TRIVIAL PROGRAMS IF YOU DO NOT USE FUNCTIONS

32. Example: Prime Numbers, Again
Write a program that:
Asks the user to enter an integer N.
Prints out the smallest prime number greater than or equal to N.
Identify the solution components
………………….

33. Example: Prime Numbers, Variation
Write a program that:
Asks the user to enter an integer N.
Prints out the smallest prime number greater than or equal to N.
Identify the solution components
Read N.
Generate ints from N up.
Stop when an int has a property (e.g. even).
??placeholder
Check if an int is prime.

34. Example: Prime Numbers, Variation
Write a program that:
Asks the user to enter an integer N.
Prints out the smallest prime number greater than or equal to N.
First step:
Write the basic structure of the program.
Put placeholders where more detail is needed.
import java.util.Scanner;
public class example1 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Enter an integer: ");
int N = in.nextInt();
int i = N;
while (i is not prime) {
i++; }
System.out.printf("%d\n", i);

35. Example: Prime Numbers, Variation
Write a program that:
Asks the user to enter an integer N.
Prints out the smallest prime number greater than or equal to N.
Second step:
Identify functions that can be used to complete the program.
We can use the is_prime function again!!!
import java.util.Scanner;
public class example1 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Enter an integer: ");
int N = in.nextInt();
int i = N;
while (is_prime(i) == false) {
i++; }
System.out.printf("%d\n", i);

36. Functions make it really easy to re-use code!!!
import java.util.Scanner;
public class example1 {
public static boolean is_prime(int N)
for (int i = 2; i < N; i++)
if (N % i == 0)
return false; }
return true;
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Enter an integer: ");
int N = in.nextInt();
while (is_prime(N) == false)
N++;
System.out.printf("%d\n", N);
Write a program that:
Asks the user to enter an integer N.
Prints out the smallest prime number greater than or equal to N.
To complete the program, we can just use the is_prime function we already have.
Functions make it really easy to re-use code!!!

37. Example Output: Example Output: Example Output:
Enter an integer:
import java.util.Scanner;
public class example1 {
public static boolean is_prime(int N)
for (int i = 2; i < N; i++)
if (N % i == 0)
return false; }
return true;
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Enter an integer: ");
int N = in.nextInt();
while (is_prime(N) == false)
N++;
System.out.printf("%d\n", N);
Example Output:
Enter an integer:
Example Output:
Enter an integer: 7500
7507

38. Making Code Easier to Read
Often times, we need to perform a task many times.
Copying and pasting code can work, but has disadvantages:
The resulting code can look long and ugly.
If we make a mistake, we end up copying and pasting the mistake many times.
Fixing such mistakes, that have been copied and pasted many times, can be a pain.
Write a function instead

39. Example: Repeated Printing
Write a program that:
Asks the user to enter a string S.
Asks the user to enter a number N.
Prints N times string S.
Enter string S: hello
Enter integer N: 5
hello
Example Output:

40. Example: Repeated Printing
Write a program that:
Asks the user to enter a string S.
Asks the user to enter a number N.
Prints N times string S.
Let's write a function, that:
takes as input a string S and an integer N.
prints the string N times.
import java.util.Scanner;
public class example1 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.printf("Enter string S: ");
String S = in.next();
System.out.printf("Enter integer N: ");
int N = in.nextInt();
//print String S repeatedly, N times. }

41. Example: Repeated Printing
The complete program is shown on the right.
Function repeat_print has two features we have not seen before:
It takes two arguments.
It returns nothing.
import java.util.Scanner;
public class example1 {
public static void repeat_print(String message, int times)
for (int i = 0; i < times; i++)
System.out.printf("%s\n", message); }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Enter string S: ");
String S = in.next();
System.out.printf("Enter integer N: ");
int N = in.nextInt();
repeat_print(S, N);

42. A Function That Returns Nothing
Function repeat_print does something useful.
However, we do not want any value returned from the function.
In that case, we specify the return type of the function as void.
import java.util.Scanner;
public class example1 {
public static void repeat_print(String message, int times)
for (int i = 0; i < times; i++)
System.out.printf("%s\n", message); }
public static void main(String[] args)
Scanner in = new Scanner(System.in);
System.out.printf("Enter string S: ");
String S = in.next();
System.out.printf("Enter integer N: ");
int N = in.nextInt();
repeat_print(S, N);

43. The main Function
When Java executes a program, how does Java know where to start?
Every program must have a function called main, such that:
It takes one argument, of type String []. We will understand this type in our next topic, when we do arrays.
the return type is void.
Until we saw how to write functions, all our code used to go to main.
Now that we have started using functions, the main code will be a relatively small part of the program.
Functions will do the bulk of the work.

44. Function Arguments Functions have arguments.
To call a function XYZ, you write something like : XYZ(argument_1, …, argument_N)
How would you know how many arguments to use?

45. Function Arguments Functions have arguments.
To call a function XYZ, you write something like: XYZ(argument_1, …, argument_N)
How would you know how many arguments to use?
From the function definition, which (among other things) defines EXACTLY:
how many arguments to use.
the type of each argument.
the order of the arguments.
public static type XYZ(type_1 arg_1, …, type_N arg_N)

46. Executing a Function Call
When the body of the function starts executing, the only variables visible to the function are:
the arguments.
variables defined in the body of the function.

47. What Will This Program Do?
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);

48. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
Current line

49. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
First line to execute:

50. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello"
First line creates variable var1

51. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello"
Next line to execute:

52. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello" var2 = "goodbye"
Next line to execute:

53. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello" var2 = "goodbye"
var3 = "earth"
Next line to execute:

54. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello" var2 = "goodbye"
var3 = "earth"
var4 = "moon"
Next line to execute: function call

55. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello" var2 = "goodbye"
var3 = "earth"
var4 = "moon"
variables in foo:
var1 = ??? var2 = ???
Next line to execute: function call.
First, assign values to arguments.

56. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello" var2 = "goodbye"
var3 = "earth"
var4 = "moon"
variables in foo:
var1 = "earth" var2 = "moon"
Next line to execute: function call.
First, assign values to arguments.

57. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello" var2 = "goodbye"
var3 = "earth"
var4 = "moon"
variables in foo:
var1 = "earth" var2 = "moon"
Next line to execute: How does Java know which var1 to print?

58. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello" var2 = "goodbye"
var3 = "earth"
var4 = "moon"
variables in foo:
var1 = "earth" var2 = "moon"
Next line to execute:
Currently executing the body of foo. Only the variables of foo are visible. “earth" is printed.

59. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello" var2 = "goodbye"
var3 = "earth"
var4 = "moon"
variables in foo:
var1 = "earth var2 = "moon"
Next line to execute:
"moon" is printed.

60. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello" var2 = "goodbye"
var3 = "earth"
var4 = "moon"
variables in foo:
var1 = "earth" var2 = "moon"
Next line to execute:
Which line comes next?

61. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello" var2 = "goodbye"
var3 = "earth"
var4 = "moon"
Next line to execute:
Done with the function call.
The variables of foo disappear.

62. Step-by-step Execution
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
variables in main:
var1 = "hello" var2 = "goodbye"
var3 = "earth"
var4 = "moon"
Next line to execute:
"goodbye" is printed.

63. Summary of Program Output
public class example1 {
public static void foo(String var1, String var2)
System.out.printf("var1 = %s\n", var1);
System.out.printf("var2 = %s\n", var2); }
public static void main(String[] args)
String var1 = "hello";
String var2 = "goodbye";
String var3 = "earth";
String var4 = "moon";
foo(var3, var4);
Output:
var1 = earth
var2 = moon
var2 = goodbye

64. Practice Write functions Based on problem description:
“Write a function that takes [as argument] a string S and returns the sum of the ASCII code of the characters in it.
Write a function that takes 2 strings, a piece size, p_sz, and merges the strings in chunks of p_sz.
“Write a function that takes [as argument] a list L and returns the sum of the elements in L. If L has strings, it should return the concatenation of all the strings.”
Write a fct that takes two arguments: a String, s, and a char ,c, and removes all the occurrences of c from the string s. Test cases: s = ‘aaxyaj’, c = ‘a’ // s = “aaaaaaaa”, c = ‘a’ // s = “aaa”, c = ‘a’
return a new string with the modifications .
Based on your own choice.