1. 2/24/2019

2. value 9 8 7 6 5 4 3 2 1 subscript Example:
Declaring/initializing an array, page 408
<type>[] <name> = new <type>[<length>];
Example:
int[] numbers = new int[10];
The length can be any integer expression:
int x = 2 * 3 + 1;
int[] data = new int[x % 5 + 2];
value 9 8 7 6 5 4 3 2 1
subscript

3. Arrays are very commonly used with for loops to access each element
This is a space problem: 1st element, 2nd element, … etc, compared with the time sequence problem we mentioned earlier (1st iteration, 2nd iteration, 3rd iteration, …)
Solution: 1st iteration handles 1st element, 2nd iteration handles 2nd element, …., etc
2/24/2019

4. Methods can accept as many parameters as you like, p286.
When the method is called, it must be passed values for each of its parameters.
Multiple parameters declaration syntax:
public static void <name> (<type> <name>,
<type> <name>, ..., <type> <name>) {
<statement(s)>; }
Multiple parameters call syntax:
<name>(<expression>, <expression>, ..., <expression>);
2/24/2019

5. Declaring a method that returns a value (p298):
public static <type> <name>(<parameters>) {
<statement(s)>; }
Returning a value from a method:
return <expression>;
Example:
// Returns the given number cubed (to the third power).
public static int cube(int number) {
return number * number * number;
2/24/2019

6. Compared with the timing problem in loop: 1st, 2nd, 3rd … iterations
This is a space & timing problem: to find the redundancy of a certain part of program running at different time.
Compared with the timing problem in loop: 1st, 2nd, 3rd … iterations
Compared with the space problem in arrays: 1st, 2nd, 3rd … elements
1st, 2nd, 3rd … appearances of the same/similar procedure in your program!
2/24/2019

7. ` summing the values in an array
public static int sum (______________){ int result=0; for(int x= 0; x<____________; x++) result+=n[x]; return result; }

8. public static int sum (______________){ int result=0; for(int x= 0; x<____________; x++) result+=n[x]; return result; } n?

9. Declaring/initializing an array, page 408
<type>[] <name> = new <type>[<length>];
public static int sum (__int [ ] n__){ int result=0; for(int x= 0; x<____________; x++) result+=n[x]; return result; }

10. 0+n[0]
…+n[1]
…+n[2] …
…+n[?}
public static int sum (__int [ ] n__){ int result=0; for(int x= 0; x<____________; x++) result+=n[x]; return result; }

11. public static int sum (__int [ ] n__){ int result=0; for(int x= 0; x<__n.length_; x++) result+=n[x]; return result; }

12. finding the highest value in an array
public static int highest (int [] n ){
int result=_____________;
for(int x= ________; x<____________; x++)
if (n[x] > result) result = n[x];
return result; }

13. public static int highest (int [] n ){ int result=_____________;
Each possible position: 0, 1, 2, …, ?
public static int highest (int [] n ){
int result=_____________;
for(int x= ________; x<____________; x++)
if (n[x] > result) result = n[x];
return result; }

14. public static int highest (int [] n ){ int result=_____________;
Initialization?
public static int highest (int [] n ){
int result=_____________;
for(int x= __0___; x<__n.length___; x++)
if (n[x] > result) result = n[x];
return result; }

15. public static int highest (int [] n ){ int result=_____________;
n[0] = -1, n[1]=-2, n[2] = -3, ….
public static int highest (int [] n ){
int result=_____________;
for(int x= __0___; x<__n.length___; x++)
if (n[x] > result) result = n[x];
return result; }

16. public static int highest (int [] n ){
int result=___n[0]__________;
for(int x= __0___; x<__n.length___; x++)
if (n[x] > result) result = n[x];
return result; }

17. Write a static method called isPrime that returns whether an integer (passing by the argument of the caller) is a prime number or not. A number is "prime" if its factors are 1 and itself only. A "factor" is a number that divides another number evenly.

18. x public static boolean isPrime ( ) int { } Finding the factor?
( )
int {
Finding the factor?
2, 3, 4, 5, …, n-1 }

19. Counter-controlled loop? How many iterations? Event-control loop!
Finding the factor?
2, 3, 4, 5, …, n-1
public static
boolean
isPrime
( )
int x {
factor =2
factor ++
for ( ;x%factor!=0; ) { }
How f changes?
1st?
2nd?
3rd?
Counter-controlled loop?
How many iterations?
Event-control loop!
When to stop?
What is the 1st factor?
x % factor == 0
if (factor == x)
else }

20. public static boolean isPrime (int x ){
int factor;
for(factor = 2; x%factor != 0; factor ++);
if (factor == x) return true;
else return false; }