如何在主程序中使用子程序的布尔返回值

Question

Hey I made a subprogram which returns either true or false. Now in my main I am not able to use it in my if statement. This is how I shaped my if statement:

    Uniqueyear(year);

    if (Uniqueyear()) {
        System.out.println(year + "is unique.");
    }

    else {
        year++;
        Uniqueyear(year);
    }

}

However, when i compile my program it says " method Uniqueyear in class DistinctDigits cannot be applied to given types; required: int found: no arguments reason: actual and formal argument lists differ in length "

I am new to programming and cant seem to fix it.I also tried writing " if (Uniqueyear(year)){.. but it messes up my output. This is my subprogram in case there is some problem in my return statement or anything else:

public static boolean Uniqueyear(int a) {

    String year= Integer.toString(a);

   for (int i=0; i<year.length(); i++) {
       for(int j = i + 1; j < year.length(); j ++){
          if (year.charAt(i) == year.charAt(j)) {
              return true;
          }
       }
   }
    return false;

Any help will be appreciated. :)

Answer 1

The "subprogram" is called a method. Since it is static it is a class method (a method that is called on a class instead of on an instance, like non-static methods).

When you call Uniqueyear(year), you are calling the Uniqueyear method in that class.

You have defined one Uniqueyear method that receives an int. So whenever you call it, the compiler will expect to find an integer value passed to it.

Therefore, when you do

if (Uniqueyear()) {
}

the compiler complains that you haven't passed the required parameters to Uniqueyear.

You could store the return value of your previous call to Uniqueyear and then use the if on that value.

boolean myBoolean = Uniqueyear(year);
if (myBoolean) {
}

Or you could also, alternatively, remove the first Uniqueyear call and put it directly inside of the if condition.

if (Uniqueyear(year)) {
}