Exercise 1: 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.

Exercise 1: Strings & Numbers
1. Objective
2. Questions

Objective

Goal of this exercise is to get a basic understanding of

how to work with Strings in Java to represent arbitrary text
how to work with numbers in Java
what is a variable

Questions

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

Question 1

Given the following code:

class Main {
    public static void main(String[] args) {
        String test = "Hello World!";
        System.out.println(test);
    }
}

what do you think the code does? What does the first line in the main method mean?

Question 2

Given the following code:

class Main {
    public static void main(String[] args) {
        String test;
        test = "Hello World!";
        System.out.println(test);
    }
}

will it do the same as in question 1?

Can you assign a new String to test after the print statement? If you print test than again, what would be the output?

Question 3

Java cannot only deal with text but also work with numbers.

The following code snippet shows you the most common types for numbers in Java:

class Main {
    public static void main(String[] args) {
        int i = ?
        long l = ?
        float f = ?
        double d = ?
    }
}

do you have an idea, with what you can/need to replace each question mark? And can you print these numbers?

Question 4

Which of these statements are invalid and why?

class Main {
    public static void main(String[] args) {
        int i = "3";
        String f = 4;
        int j = 5;
        f = j;
        String g = j;
        j = "4";
    }
}