Boolean, if methods,

Question

I am a beginner in the java programming language. I wasn't able to write the code for this program because I am not an expert in boolean operators. I just wanted to know how you people out there would program this question in the book because I am unable to figure out how to get this program working without the if/else branch. Help would be appreciated, sorry if you guys are annoyed with this question.

Question in book,

Write a program that asks the user to enter a month (1 for January, 2 for February, etc.) and then prints the number of days in the month. For February, print “28 days”.

    Enter a month: 5
    30 days

Use a class Month with a method public int getLength() Do not use a separate if/else branch for each month. Use Boolean operators.

Thanks!

*I dont know how to use switch statements, I just want to be able to do it like how it says it in the book,

Thanks

Answer 1

I whould do something like this:

public class Month
{
int month;
public Month(int _month)
{
    this.month = _month;
}

public int getLength()
{
if(this.month == 2) { return 28 }
if(this.month<8)
{
    if((this.month%2) == 1)
    {
        return 31
    }
    else
    {
        return 30
    }
}
else
{
    if((this.month%2) == 1)
    {
        return 30
    }
    else
    {
        return 31
    }
}

} }

EDIT. After reading the updated question from the book i think they are looking for something like this.

public int getLength()
{
if(this.month == 2) {return 28;}
if(this.month == 1 || this.month == 3 || this.month == 5 || this.month == 7 || this.month == 8 || this.month == 10 || this.month ==12){ return 31;}
if(this.month == 4 || this.month == 6 || this.month == 9 || this.month == 11){return 30;}
}

But the answers other have given is better in a real life situation.

Answer 2

Assuming you don't need to deal with leap years, your Month class might look something like this:

public class Month {
    private int monthNumber;

    public Month(int monthNumber) {
        if (monthNumber < 1 || monthNumber > 12) {
            throw new IllegalArgumentException(
                "Month number must be between 1 and 12");
        }
        this.monthNumber = monthNumber;
    }

    public int getLength() {
        return monthLengths[monthNumber - 1]; // indexes start at 0
    }

    private static int[] monthLengths = {
        31, // January
        28, // February
        31, // March
        . . .
    }
}

The rest of the code (prompting the user, getting input, error checking, printing the answer) is left as an exercise. :)

P.S. I can't imagine where Boolean enters into this at all.

Answer 3

If you want to do something for specified numbers you can either use something like

if ( number == 1 ){ 
    doSomething();
} else if ( number == 3 ){
    doSomething();
} else if ( number == 5 ){
    doSomething();
}

But since this approach is forbidden

Do not use a separate if/else branch for each month.

Use Boolean operators.

you need to use boolean OR || operator like

if (number==1 || number == 3 || number == 5){
    doSomething();
}

Now try to use this for months.

Answer 4

Use a map with the key being the integer value input from the user and the value being the number of days in that month. For example:

Hashmap<Integer, Integer> map = new Hashmap<Integer, Integer>();
map.put(1, 31);
...
map.put(12, 31);

Then ask for input and do something like:

int input = ...;
if (map.containsKey(input)) {
    System.out.println(map.get(input));
}
else {
    System.out.println("Invalid month input");
}