study-sheet.md

Study Sheet

Midterm

Tips

• Write the method header first, with the correct return value, name, and parameters along with open curly brace and closing curly brace (this will usually earn you a minimum of 1pt)
• Complete problems 1 – 7, write the method header for 8 (the hard programming problem) and any other details you know are in the solution (loop, if block, return statement, etc.), then go back and check your solutions for 1 – 7, and finally work on the solution for 8.
• If you cannot solve a programming problem, solve a simpler version instead (this will earn you lots of partial credit)
• Do not open your test before told to begin, and stop writing when time is called; don't lose these points .. its never worth it.
• Do not abbreviate anything on the exam, except for A/S/N on the assertion questions

Reminders

• Know where your seat is before you arrive
• Bring your ID
• Bring pencils, not pens (and optional highlighter—recommended!)
• Do not bring calculators or other electronics
• Turn in your exam when you are done and leave the room

Concepts

You should plan to be fully prepared for everything listed below

Using Random objects

Random r = new Random();
r.nextInt(10); // 0 – 9
r.nextInt(10) + 1; // 1 – 10
r.nextInt(30) + 10; // 10 – 39
r.nextInt(5) - 2; // -2 – 2

Using Scanner objects

Scanner console = new Scanner(System.in);
String word = console.next(); // reads in as a String; all characters
int x = console.nextInt(); // reads in as an int
double y = console.nextDouble(); // reads in as a double

Solving fencepost problems

Tips: Usually needs a loop.

// Print out the values x – y (inclusive) in a comma separated list
public static void printList(int x, int y) {
  // print first value before the loop
  System.out.print(x);
  // loop through the rest, printing comma first; notice i starts +1 of x
  for (int i = x + 1; i <= y; i++) {
    System.out.print(", " + i);
  }
  System.out.println();
}

Solving cumulative sum problems

Tips: Usually needs a sum variable, a loop, and an update variable statement inside of the loop.

// Return sum of int values x – y (inclusive); ignoring Gauss : [
public static int sum(int x, int y) {
  // declare a sum variable
  int sum = 0;
  // loop through values, adding to sum
  for (int i = x; i <= y; i++) {
    sum = sum + i;
  }
  return sum;
}

Solving counting problems

Tips: Usually needs a count variable, a loop, and an increment statement inside the loop.

// return the number of values entered by the user greater than max
// the user will enter -1 to stop
public static int greaterThan(int max) {
  Scanner console = new Scanner(System.in);
  System.out.print("Enter a number (-1) to quit: ");
  int num = console.nextInt();
  int count = 0;
  while(num != -1) {
    if (num > max) {
      count++;
    }
    System.out.print("Enter a number (-1) to quit: ");
    int num = console.nextInt();
  }
  return count;
}

Finding the max and min in a set of values

Tips: Usually needs a min variable and a max variable, a loop, and if statements inside the loop.

// Print the max and min of the values entered by the user
// the user will enter 0 to stop
public static void maxMin() {
  Scanner console = new Scanner(System.in);
  System.out.print("Enter a number (0) to quit: ");
  int num = console.nextInt();
  int max = num; 
  int min = num;
  while(num != 0) {
    if (num > max) {
      max = num;
    } else if (num < min) {
      min = num;
    }
    System.out.print("Enter a number (0) to quit: ");
    int num = console.nextInt();
  }
  System.out.printf("Max: %d Min: %d\n", max, min);
}

Being able to look at the individual digits of a number using integer arithmetic

Tips: Look through the number from right – left, not from left – right

// Return the smallest digit in a number
public static int smallestDigit(int value) {
  // special case; if 0 is passed as value
  if (value == 0) {
    return 0;
  }
  int min = 10; // no digit bigger than 9
  while (value != 0) {
    int digit = value % 10;
    if (digit < min) {
      min = digit;
    }
    value = value / 10;
  }
  return min;
}

Being able to look through the individual characters in a String

Tips: Usually needs a for loop that goes until the length of the String

// return the String will all a's removed
public static String removeAs(String word) {
  String output = "";
  for (int i = 0; i < word.length(); i++) {
    char letter = word.charAt(i);
    if (letter != 'a') {
      output = output + letter;
    }
  }
  return output;
}