Lecture #10

Announce
- Continue to Read Chapter 3

Numerical Computation and the Study of Functions

Loops!! ... and it all happened again ...
The while Loop

while (boolean expression) { statement; ... statement;
}
- For proper loop: at least one of previous statements must cause change in logical expression
Looping Examples: Gauss Problem

int sum = 0; int k = 0; while (k < 100) { k = k + 1; sum = sum + k;
}
Looping Example
CompInterest.java, CompInterest.html
Looping Example
Diamond.java, Diamond.html
Other Loops Designs
- Data Dependent Loop
Redesign of Diamond Program
- Use of Magic Numbers
Arrays, Motivation
- Required for:
  - required for dealing with lists
Have Multiple Elements or Cells
Use Subscript or Index to Identify Element
- Subscripts are usually integers in brackets
x[5] = 21;
---.setText("Result is " + x[5]);
Use Arrays in a Loop

int k = 0; sum = 0; while ( k < 10 ) { k = k + 1; sum = sum + name[k];
}

Array Creation and Use

int num[] = new int[6];
+--+--+--+--+--+--+
| ?| ?| ?| ?| ?| ?|
+--+--+--+--+--+--+
  0  1  2  3  4  5 


num[1] = 21; num[5] = 13;
+--+--+--+--+--+--+
| ?|21| ?| ?| ?|13|
+--+--+--+--+--+--+
  0  1  2  3  4  5 

int k = 2;
while(k<6){num[k] = k*k; k = k+1;}
+--+--+--+--+--+--+
| ?|21| 4| 9|16|25|
+--+--+--+--+--+--+
  0  1  2  3  4  5

Setting it Up

Declaration:
double weights[];
Definition:
weights = new double[50];
Or Combined:
double weights[] = new double[50];
Subscript Range!!!
Simple Examples
Real Array Example
Hotel.java, Hotel.html