double r = Math.random();
while (r < 0.5) {
    r = Math.random();
}

int num = 1;
while (num < 200) {
    System.out.print(num + " ");
    num *= 2;
}
System.out.println(num);

1 2 4 8 16 32 64 128 256

Random randomObject = new Random();
int randomNumber = randomObject.nextInt(10);

import java.util.*;
public class RollDice {
    public static void main(String[] args) {
        Random rand = new Random();
        int sum = 0;
        while (sum != 7) {
            int roll1 = 1 + rand.nextInt(6);
            int roll2 = 1 + rand.nextInt(6);
            System.out.println("The dice are " + roll1 + " and " + roll2);
            sum = roll1 + roll2;
        }
    }
}

1, 2, 3, 4, 5

System.out.print(1);
for (int i = 2; i <= MAX_NUMBER; i++) {
    System.out.print(", ");
    System.out.print(i);
}

for (int i = 1; i < MAX_NUMBER; i++) {
    System.out.print(i);
    System.out.print(", ");
}
System.out.print(MAX_NUMBER);

for (int i = 1; i <= MAX_NUMBER; i++) {
    System.out.print(i);
    if (i < MAX_NUMBER) {
        System.out.print(", ");
    }
}

Scanner console = new Scanner(System.in);
int sum = 0;
System.out.print("Enter first integer (-999 to quit): ");
int value = console.nextInt( );
while (value != -999) {
    sum += value;
    System.out.print("Enter next integer (-999 to quit): ");
    value = console.nextInt( );
}
System.out.print("The sum is " + sum);

Scanner console = new Scanner(System.in);
System.out.print("Enter your age: ");
int age = console.nextInt( );
boolean tobaccoLegal = (age >= 18);
if (tobaccoLegal) {
    System.out.println("You can buy tobacco.");
} else {
    System.out.println("You can't buy tobacco.");
}
boolean alcoholLegal = (age >= 21);
if (alcoholLegal) {
    System.out.println("You can buy alcohol.");
} else {
    System.out.println("You can't buy alcohol.");
}

Scanner console = new Scanner(System.in);
String answer = "yes";          // priming the loop
while (answer.equals("yes")) {  // don't use == with Strings
    System.out.print("Enter yes to continue: ");
    answer = console.next( );
}
System.out.print("Are you sure you want to stop? ");
answer = console.next( );
while (answer.startWith("n")) {
    System.out.print("Are you sure yet? ");
    answer = console.next( );
}

public static boolean bothOdd1(int a, int b) {
    if (a % 2 == 1) {
        if (b % 2 == 1) {
            return true;
        }
    }
    return false;
}

public static boolean bothOdd2(int a, int b) {
    if (a % 2 != 1) {
        return false;
    }
    if (b % 2 != 1) {
        return false;
    }
    return true;
}

public static boolean bothOdd3(int a, int b) {
    if (a % 2 == 1 &&b % 2 == 1) {
        return true;
    } else {
        return false;
    }
}

public static boolean bothOdd4(int a, int b) {
    return (a % 2 == 1 && b % 2 == 1);
}

(answer.charAt(2) == 's')

(answer.length() >= 3 && answer.charAt(2) == 's')

(score >=0 && score <= 100)
(answer == 'y' || answer == 'Y')

(! (score >=0 && score <= 100))
(! (answer == 'y' || answer == 'Y'))

Scanner console = new Scanner(System.in);
System.out.print("Enter a nonnegative number: ");
double num = console.nextDouble( );
while (num < 0) {
    System.out.print("Invalid number, try again: ");
    num = console.nextDouble( );
}
double root = Math.sqrt(num);
System.out.print("The square root of " + num + " is " + root);

Scanner console = new Scanner(System.in);
System.out.print("Enter an int: ");
while (! console.hasNextInt( )) {
    String trash = console.next( );
    System.out.println("You did not enter an int: " + trash);
    System.out.print("Enter an int: ");
}
int keeper = console.nextInt( );
System.out.println("You entered an int: " + keeper);

Scanner console = new Scanner(System.in);
boolean continueLoop = true;
double num = -1;  // need to declare num outside the loop
System.out.print("Enter a nonnegative number: ");
while (continueLoop) {
    if (console.hasNextDouble( )) {
        num = console.nextDouble( );
        if (num >= 0) {
            continueLoop = false;
        }
    } else {
        String trash = console.next( );
    }
}
double root = Math.sqrt(num);
System.out.print("The square root of " + num + " is " + root);

if (x > 3) { 
    // Point A 
    x--; 
} else { 
    // Point B
    x++;
} 
// Point C

System.out.print("Type a nonnegative number: ");
double number = console.nextDouble(); 
// Point A: is number < 0.0 here? (SOMETIMES)
while (number < 0.0) { 
    // Point B: is number < 0.0 here? (ALWAYS)
    System.out.print("Negative; try again: "); 
    number = console.nextDouble(); 
    // Point C: is number < 0.0 here? (SOMETIMES)
}
// Point D: is number < 0.0 here? (NEVER)

int x = 3;
// is x > 0? ALWAYS

public static void mystery(int a, int b) { 
    // is a == 10? SOMETIMES
    ...
}

public static void mystery(int a, int b) {
    if (a < 0) {
        // is a == 10? NEVER
        ... 
    }
    ...
}

while (y < 10) { 
    // is y < 10? ALWAYS
    ...
}

while (y < 10) { 
    y++;
    // is y < 10? SOMETIMES
    ...
}

while (y < 10) { 
    ...
}
// is y < 10? NEVER