ENGR 131: For in Action

Repeat N times

Roll Die 7 times

int rolls;

for (rolls=0; rolls<7; rolls++) {
  System.out.println((int) (Math.random()*6)+1);
}

Count from 0 to 100

int i;

for (i = 0; i<=100; i++) {
  System.out.println(i);
} 

Count from 0 to 100 by 5s

int i;

for (i = 0; i<=100; i+=5) {
  System.out.println(i);
} 

Count from 0 to 100 by 10s

int i;

for (i = 0; i<=100; i+=10) {
  System.out.println(i);
} 

Count from 0 to 100 by 12s

int i;

for (i = 0; i<=100; i+=12) {
  System.out.println(i);
} 

Count Down to Liftoff

int i;

for (i = 10; i>0; i--) {
  System.out.print(i+" ... ");
} 
System.out.println("Liftoff!");

Tables of Functions

Square Roots for 0 through 15

int i;

System.out.println("i \tsqrt(i)");
for (i = 0; i<16; i++) {
  System.out.println(i+":\t"+Math.sqrt(i));
}

sin and cos of x for Multiples of PI/4

int i;

double d, x;
System.out.println("x \t sin(x) \t cos(x)");
d = Math.PI/4.;

for (i = 0; i<8; i++) {
  x = d * i; 
  System.out.println(x+"\t"+Math.sin(x)+"\t"+Math.cos(x));
} 

Sums

Sum of the First 15 Integers

int i;

int sum;

sum = 0;
for (i = 1; i<=15; i++) {
  sum += i;
} 
System.out.println(sum);

Sum of the First N Integers

int i;

int sum, N;

// N is set somewhere in here

sum = 0;
for (i = 1; i<=N; i++) {
  sum += i;
} 
System.out.println(sum);

Sum of the First N Squares of Integers

int i;

int sum, N;

// N is set somewhere in here

sum = 0;
for (i = 1; i<=N; i++) {
  sum += (i*i);
} 
System.out.println(sum);

Sum of the First N+1 Terms of a Geometric Series

// sum_{i = 0 to N} r^i
int i;

int N;
double sum, term;

// N is set somewhere in here

sum = 0;
term = 1.0;
for (i = 0; i<=N; i++) {
  sum += term;
  term *= r;
} 
System.out.println(sum);

Functions Involving Repetition

Compute n! for n >= 0

int i;

int answer, n;

// n is set somewhere in here

answer = 1;   // 0! == 1
for (i = 1; i<=N; i++) {
  answer *= i;
} 
System.out.println(answer);

Computes 2^n for n >= 0

int i;

int answer, n;

// n is set somewhere in here

answer = 1;   // 2^0 == 1
for (i = 1; i<=n; i++) {
  answer *= 2;
} 
System.out.println(answer);

computes m^n for n >= 0

int i;

int answer, n;

// n is set somewhere in here

answer = 1;   // m^0 == 1
for (i = 1; i<=n; i++) {
  answer *= m;
} 
System.out.println(answer);