CS160: Foundations in Programming: Summer 2016

• Take a written quiz reviewing topics from last week.
• Review switch statements.
• Review if, else if, and else statements.
• Understand the similarities and differences between the two.
• Learn about logical comparison operators and logical operators.
• Practice reading code.
• Complete a set of exercises through Hackerrank.
• Write a simple calculator program.

public static void main (String [] args) {

    int num = 3;
    if (num != 3)
        System.out.println("Num is not 3");
        num = 3;
        System.out.println("Num is now 3");
    else
        System.out.println("Num has always be 3");

} 

public static void main (String [] args) {

    String s0 = "Hello";
    String s1 = "Hello";
        if (s0 == s1)
            System.out.println("s0 and s1 are the same!");
	else
	    System.out.prinlnt("s0 and s1 are NOT the same!");

} 

public static void main (String [] args){

    char c = '@';
    switch (c) {
        case '@': System.out.println("char c = '@'");
        case '$': System.out.println("char c = '$'");
        case '4': System.out.println("char c = '4'");
        case 'u': System.out.println("char c = 'u'");
        case ' ': System.out.println("char c = ' '");
        default: System.out.println("char c is not '@', '$', '4', 'u', ' '");
    }

} 

public static void main(String[] args) {

    int month = 2;
    int year = 2000;
    int numDays = 0;

    switch (month) {
        case 1: case 3: case 5:
        case 7: case 8: case 10:
        case 12:
            numDays = 31;
            break;
        case 4: case 6:
        case 9: case 11:
            numDays = 30;
            break;
        case 2:
            if (((year % 4 == 0) && !(year % 100 == 0)) || (year % 400 == 0))
                numDays = 29;
            else
                numDays = 28;
                break;
        default:
            System.out.println("Invalid month.");
            break;
    }
    System.out.println("Number of Days = " + numDays);

}

• Log into Hackerrank
• Complete the section named R2
• These practice problems will be open after this recitation as an additional resource.
• Remember, you can use the examples from this recitation and the lecture notes.

• Create a new Java Project named R2, and make a class named R2.
  
  • Make sure to select the public static void main(String[] args) method stub when you create each class.
• Copy the following code into the main method and follow the specifications:

    Scanner keyboard = new Scanner(System.in);

    //Prints a welcome message
    System.out.println("Welcome to a simple calculator program!");
    System.out.println("---------------------------------------");
    System.out.println("All we know how to do is add, subtract, multiply, " +
	    	       "divide, compute modulo and calculate exponential expressions.");
    System.out.println();

    // Get input from the user
    System.out.print("Please enter a the first number of your calculation: ");
    double d1 = keyboard.nextDouble();

    System.out.print("Please enter the operator (+|-|*|/|%|^): ");
    // 1. ADD code here

    System.out.print("Please enter a the second number of your calculation: ");
    // 2. ADD code here

    // Here we will calculate the result:
    double result;

    // 3. ADD code here

    // Print the result
    System.out.println("---------------------------------------");
    // 4. ADD code here

    System.out.println("---------------------------------------");

    keyboard.close();

1. Create a variable of type character and use the Scanner object to store the operator.
• Your TA will show you how to get a character from the Scanner object.
2. Create a variable of type double and use the Scanner object to store the second number.
3. Write a switch statement that calculates the result and stores it in the double variable previously declared.
• The operator '%' is used to calculate the remainder of a problem after division. Example 4 % 3 = 1.
  • Learn more about the modulo here.
  • Solve some practice problems here.
• The operator: '^' is used to raise a number to a power. Example: 3 ^ 4 = 81.
• You will want to use Math.pow(number, exponent) to do this calculation.
4. If you're curious about exponential math, you can read more here.
5. Print the result to 2 decimal places using printf.
6. In the switch statement figure out a way to gracefully handle the user typing in a bad operator (like '@'). Print "Bad user input." and end the program.
7. In the switch statement figure out a way to print "Cannot divide by zero." when the user tries to divide by zero.

Correct Output

Welcome to a simple calculator program!
---------------------------------------
All we know how to do is add, subtract, multiply, divide, compute modulo and calculate exponential expressions.

Please enter a the first number of your calculation: 5
Please enter the operator (+|-|*|/|%|^): +
Please enter a the second number of your calculation: 8.7
---------------------------------------
Result:
5.00 + 8.70 = 13.70
---------------------------------------

Dividing by Zero

Welcome to a simple calculator program!
---------------------------------------
All we know how to do is add, subtract, multiply, divide, compute modulo and calculate exponential expressions.

Please enter a the first number of your calculation: 4
Please enter the operator (+|-|*|/|%|^): /
Please enter a the second number of your calculation: 0
Cannot divide by zero.

Incorrect Operator

Welcome to a simple calculator program!
---------------------------------------
All we know how to do is add, subtract, multiply, divide, compute modulo and calculate exponential expressions.

Please enter a the first number of your calculation: 8
Please enter the operator (+|-|*|/|%|^): &
Please enter a the second number of your calculation: 6
Bad user input.