最后在for循环中打印一次语句？

Question

I have a for loop with an if statement inside and I want the statement to print after all the iterations have occurred but it prints after each iteration for which the if statement applies. I want the program to go through the iterations and whatever names start with the letter inputted, I want them to print with the statement "The last names that start with " + letter + " are " + students[i]" only once at the end. Is there a way to do that?

    import java.util.Scanner;

public class ClassNames {

   public static void main(String[] args) {

   Scanner keyboard = new Scanner(System.in);

   int numberOfStudents;
   int i;

   System.out.print("Please enter the total number of students: ");
   numberOfStudents = Integer.valueOf(keyboard.next());

   String students[] = new String[numberOfStudents];

   i = 0;
   while(i < numberOfStudents) {
      System.out.print("Enter the last name: ");
      students[i] = keyboard.next();
      i++;
   }   

   String findName;
   System.out.print("Enter a name to search for: ");
   findName = keyboard.next();


   for(i = 0; i < numberOfStudents; i++) {

      if(students[i].contains(findName)) {
      System.out.println(findName + " is at index " + i);
      }
       else {
      System.out.println("That name does not exist ");
      break;
      }
   } 

   String letter;

   System.out.print("Enter a letter to search on: ");
   letter = keyboard.next();

   for(i = 0; i < numberOfStudents; i++) {

      if(students[i].startsWith(letter)) {
         System.out.println("The last names that start with " + letter + " are " + students[i]);

      }
   }

   }
}  

Answer 1

You can just print "The last names that start with " + letter + " are " before the for loop and use the loop to print the student names.

System.out.println("The last names that start with " + letter + " are ");
for(i = 0; i < numberOfStudents; i++) {
      if(students[i].startsWith(letter)) {
         System.out.print(students[i] + ","); // Comma to separate student names
      }
   }

Hope this helps and what you were looking for.

Answer 2

Perhaps something like the following is what you want:

System.out.print("The last names that start with " + letter + " are ");
for (i = 0; i < numberOfStudents; i++) {
   if (students[i].startsWith(letter)) {
      System.out.print(students[i] + ", ");
   }
}
System.out.println();

This will leave with you a trailing comma, but might get you on the road to where you want to be.

Answer 3

You are printing out the output before you know the result.

Get the result, and then generate the output. We need to store which names were a match, and display them with one print out. An ArrayList works nicely for this, since we don't know how many names are a match until we are finished looping, which works better than creating an array with a set size that could be too large or too small.

List<String> matchesFound = new ArrayList<>();
for (i = 0; i < numberOfStudents; i++) {
    if (students[i].startsWith(letter)) {
        matchesFound.add(students[i]);
    }
}

if (!matchesFound.isEmpty()) {
    System.out.printf("The last name(s) that starts with %s %s %s.", letter,
         matchesFound.size() > 1 ? "are" : "is", String.join(", ", matchesFound));
}

Answer 4

Let me try to answer your question as much as I understand your question, You have two kinds of search: with name and with the first letter.

First of all, if you want to perform a string equality check, better to use .equals or .equals vs .equalsIgnoreCase such that

if(students[i].equals(findName))

I will focus on your question and answer for just letter search part. (as search name part is also problematic as it will print else section for each iteration as long as it can not find the name)

So, if you want to print all name starting with letter 'x' (let's assume letter is x) then first, you need to iterate all your names first and save whenever you find a match. You can save those name by using different collections. You can use ArrayList for this specific purpose.

  String letter;
   ArrayList<String> matches = new ArraList<String>();
   System.out.print("Enter a letter to search on: ");
   letter = keyboard.next();

   for(i = 0; i < numberOfStudents; i++) {

      if(students[i].startsWith(letter)) {
         matches.add(students[i]);

      }
   }
String names = "";
if(!matches.isEmpty)
{
  for(String name : matches)
  { 
    names += name + " "; 
 }
 System.out.println("The last names that start with " + letter + " are " + 
    names);
}