Jam 1: Study Guide

Jams are open book. 40 minutes in lab.

Topics:

Variables: defining and assigning
Data types: String, double, int
Command line variables
System.out.println(), System.out.print()
System.console().readLine()
arithmetic operators: +, *, -, /, %
String concatenation with +
math utilities: sqrt, pow, cos, sin, exp, log, random, etc
Operators and expressions, order of operations

Write Java programs to check your answers. Or you can ask a TA or instructor to give feedback on your responses.

Practice questions

1) What is the value and type for each of the following expressions?

2 + 3
Math.pow(2, 3)
2.0 + 3
5.5/10
5 - 2 * 3
"123"
48 % 2
2.0
2+4*2+1
"lol" + "cats"

2) Write a program Sum.java that takes two command line arguments, converts them to integers and outputs their sum. You can assume that the command line arguments are both valid integers.

$ java Sum 4 5
The sum is 9.

$ java Sum 0 0
The sum is 0.

$ java Sum -1 5
The sum is 4.

3) Write a madlib program that asks the user for 2 colors and one adjective, then prints out the filled-in poem:

$ java Roses
color: pink
color: azure
adjective: funny

Roses are pink
Violets are azure
Sugar is funny
and so are you!

4) Write a program that takes a user’s hotel room rate and outputs the cost of a 6% sales tax and 10.5% city tourism fee. The program should then output the total bill.

$ java Bill
Room rate: 100
Total nights: 3
-------------------
Tax: $ 18.0
Tourism Fee: $ 31.5
Total: $ 349.50

5) What is the output of the following program?

public class Cats {
   public static void main(String[] args) {
       String type = "tuxedo";
       int fish = 3;

       System.out.println("The "+type+" cat caught "+fish+" fish.");
   }
}

6) The following program has several problems. What are they? For each error, is the error a syntax error, runtime error, or logic error? How can we fix the problem?

public class Mystery {
    public static void main(String args) {
        System.out.print("Enter a value: ");
        String valueStr = System.console().readLine();
        int value = Integer.parseInteger(valuStr);
        int result = value * 10
        System.out.println("The result is "+result);
    }
}

7) The following program has a problem. What is it? Is the error is syntax error, runtime error, or logic error? How can we fix the problem?

public class Mystery {
    public static void main(String[] args) {
        int value = Integer.parseInt(args[0]);
        double fraction = value / 10;
        System.out.println("The fraction is "+fraction);
    }
}

8) The following program has a bug. Is the error is syntax error, runtime error, or logic error? How can we fix the problem?

public class Mystery {
    public static void main(String[] args) {
        int value = Integer.parseInt(args[0]);
        double fraction = value / 0;
        System.out.println("The fraction is "+fraction);
    }
}