Working with strings - Public int length()

Question

I'm completely new to programming, and I'm having difficulties understanding my assignment, and how I proceed solving it.

The assignment is introduced by saying: The String class defines a length accessor method with the following header: public int length() So the following is an example of its use with the String variable fullName; fullName.length()

The assignment then asks me to add conditional statements to the constructor of Student to print an error message if either the length of the fullName parameter is less than four characters or the length of the studentId parameter is less than three characters. However, the constructor should still use those parameters to set the name and id fields, even if the error message is printed.

The assignment also suggests that use if and else methods.

I've read up on everything until this point, but I simply don't understand how I proceed - I do, however, understand what it's supposed to function.

Can you guys perhaps lead me the way, or just give some hints on how I get started on this? It's noteworthy to mention that this is coded in BlueJ, and it's using an example of the project "LabClass".

Answer 1

Let's first initialize object of your class Student leaving error checks aside. As you said, you are obliged to set these two fields (fullName and studentId) no matter what. So thats what we would have:

public class Student {

    private String studentId;
    private String fullName;

    public Student(String studentId, String fullName) {
        this.studentId = studentId;
        this.fullName = fullName;
    }

    public static void main(String[] args) {
        Student s = new Student("12", "John Doe");
    }
}

Above code does what you need in the first place. I hope you understand what is going on there? If not, then ask.

OK, what do we need now is adding this "length check". The key is to understand "if" construct. "If" allows you to execute some block of code only if certain condition is met. Condition may be any expression, but it must be evaluated to "true" or "false" (it needs to be boolean). "If" construct looks like this:

if (expression) {
    System.out.println("Expression was true!");
}

You can put in place of "expression" your condition and if happens it is true, the code will be executed. See this:

if (3 > 2) {
    System.out.println("Three is greater than two");
}

Well, we can use this knowledge to perform our length tests:

if (fullName.length() < 4) {
    System.err.println("Name '" + fullName + "' is too short");
}

Use the same construct (but different condition) to test studentId. I believe you should be able to modify the original source to check for string lengths.

As to this assignment --- you don't need else construct in this case, but to be complete: you can use it in combination with "if", to execute certain code, when the condition is not met, like this:

if (fullName.length() < 4) {
    System.err.println("Too short!");
}
else {
    System.out.println("OK");
}

Hope this helps.

Answer 2

I'd say the best thing you could do is start coding and see what happens. You mentioned that you were worried you would ruin something. You can't break anything by making mistakes, in fact, making mistakes is how all of us learn to do this. Try something and if it doesn't work, the computer will tell you what's wrong with it. Sometimes what the computer tells you doesn't make a lot of sense, but it will at least give you a starting point. The dialog between you and the computer is how you learn what works and what doesn't.

You're also worried about being stuck in something you don't understand. Nobody understands these things at first, and since there's always more to learn than any one person could possibly know, all programmers have to deal with a certain amount of confusion. You have to trust that if you sit down and start working at it that the confusion will clear. The best way to learn a new language is to speak it, and the advantage of programming is computers have infinite patience with your mistakes.