Question

Here is the code:

class Time {
public static void printTime (int hour, int minute) {
System.out.print (hour) ;
System.out.print (":") ;
System.out.print (minute) ; 
} 

public static void main (String[] args) {
hour = 11 ; 
minute = 30 ;
printTime () ; 

}
}

Here is what terminal says when I try to compile it:

david-allenders-macbook-pro:~ davidallender$ Javac Time.java
Time.java:9: cannot find symbol
symbol  : variable hour
location: class Time
hour = 11 ; 
^
Time.java:10: cannot find symbol
symbol  : variable minute
location: class Time
minute = 30 ;
^
Time.java:11: printTime(int,int) in Time cannot be applied to ()
printTime () ; 
^
3 errors
david-allenders-macbook-pro:~ davidallender$ 

I’m in the process of learning so I don’t really know what’s going on. Right now I’m in the section in the book about parameters in/on/within/above/preposition (I’m not sure what the right preposition is) methods.

• What does a parameter do?
• Why is it useful?
• What did I do wrong in the above code?
• What did the error message mean?

Answer 1

Parameters give a method information it needs to do its job. For example, a function to find the square root of a number would have that number as a parameter.

You need to pass arguments to give the parameters values. So instead of trying to set minute and hour in the main method, you need to call

printTime(11, 30);

As a sort of meta-comment, this is the kind of thing you tend to learn pretty early – and while sites like this can help you with specific questions, you’d be better off reading a good entry level book about Java. If you’re already reading a book but it didn’t describe parameters clearly, you might want to think about getting another book 🙂