Exercise 1: Operators on Strings & Numbers

Please do this exercise in a group with other students.

Go through the questions and discuss the answers within your group. Write them down/remember them to share later with the class.

1. Exercise 1: Operators on Strings & Numbers
   1. Objective
   2. Questions
      1. Question 1
      2. Question 2
      3. Question 3
      4. Question 4

Objective

Goal of this exercise is to get to know

• how to handle / deal mathematical operations with numbers in Java
• how to concatenate Strings
• how to compare numbers

Questions

Try to find the answers within your group (in case of questions/problems => ask one of your teachers!)

Question 1

If you have numbers, you should also be able to use them in mathematical operations.

Can you guess how to write a program that does

• addition
• subtraction
• multiplication
• division
• modulo (i.e. return the remainder value of a division, e.g. 7 % 2 returns 1)

of numbers?

How would you assign the result of these operations to a variable and print it?

Question 2

Given the following snippet

class Main {
    public static void main(String[] args) {
        String a = "A";
        String b = "B";
    }
}

how can you change the program to print out

• AB
• BA
• ABBA

by only using these variables?

Question 3

Given the following program

class Main {
    public static void main(String[] args) {
        int i = 1;
        int j = 2;
        String k = "a";
        System.out.println(i + j + k);
        System.out.println(i + k + j);
        System.out.println(k + i + j);
    }
}

what will it print?

what can you conclude from this?

Question 4

Let’s try some more operations with numbers:

Given two numbers, try to compare them

• what kind of comparisons exist?
• can you find out how to do comparisons of two numbers in Java?
• can you assign the result of such a comparison to a variable?