Increment array index for input

You should really avoid doing it like this, and take an OOP approach instead.

public class Student
{
    private String firstName;
    private String secondName;

    public Student(String firstName, String secondName)
    {
        this.firstName = firstName;
        this.secondName = secondName; 
    }
}

Then you can simply create an array of type Student, and populate it as you want.

Example

Student[] students = new Student[10];
int position = 0;

String firstName = scanner.readLine();
String secondName = scanner.readLine();

students[position++] = new Student(firstName, secondName);

And even simpler would be to use a List implementation.

Example

List<Student> students = new ArrayList<Student>();
String firstName = scanner.readLine();
String secondName = scanner.readLine();
students.add(new Student(firstName, secondName));

If you must use an Array

You need some form of a placeholder to keep your position within the array.

int position = 0;

You also need an input mechanism, that we will assume is scanner.

studentNamesArray[position++] = scanner.readLine();

What this will do is return the value of position (which at the moment is 0) and then increment it, making it 1.

This will prevent it from overwriting names in the array because the index is always increasing directly after assignment.

You can use an ArrayList and check the size that way. That way, you're not stuck with null values if user stops before 10.

ArrayList<String> names = new ArrayList<String>();

Scanner scanner = new Scanner(System.in);
String input = "";
String name;

while (names.size() < 10) {
    if (input.equalsIgnoreCase("no") break;

    System.out.println("Enter an name: ");
    name = input.nextLine();

    names.add(name);

    System.out.println("Would you like to continue?");
    input = scanner.nextLine();

}

Sure, I'll do your homework!

Coded in this text box -- i'll leave fixing it for you.

public class HomeWorkAssignment {

    public static void main( String... args ) throws Exception {

        String arrayOfNames = new ArrayOfNames[10];
        Scanner scanner = new Scanner(System.in)

        for( int i = 0; i < arrayOfNames.length; i++ ) {
            if( scanner.hasNextLine() ) {
                String studentName = scanner.nextLine();
                arrayOfNames[i] = studentName;
            } else {
                break;
            }
        }

        System.out.printf( "Names: %s", Arrays.toString( studentNames ) )

    }

}

I didn't thoroughly read your post but I have the feeling that it would be better to use a List<String> and add the student names as they are entered. Afterwards you just query the list for its size to get the number of names entered.

It's something like this pseudo code:

List<String> names = new ArrayList<>();

while( names.size() < 10 ) {
  String name = //ask the user for another name
  if( meetsCondition(name) ) {
    names.add( name );
  } 

  //maybe also add an option to enter less names, e.g. ask the user
  if( userWantsToFinish() ) {
    break;
  }
}

int numNamesEntered = names.size();

If you really have to use an array, replace the list with the array and track the number of names separately:

String[] names = new String[10]; 
int numNamesEntered = 0 ;    

while( numNamesEntered < names.length ) {
  String name = //ask the user for another name
  if( meetsCondition(name) ) {
    names[numNamesEntered] = name;
    numNamesEntered++; //for clarity, could also be done in the line above
  } 

  //maybe also add an option to enter less names, e.g. ask the user
  if( userWantsToFinish() ) {
    break;
  }
}    

So if I understand you correctly, what you want to do is about the following:

if (containsName(studentNamesArray, studentName) == false) {
  addStudent(studentNamesArray, studentName);
}

Besides that this could be easily solved with a Java Set like this:

studentSet.add(studentName); // automatically ignores duplicates

all you need to do for the first code part is to write the functions containsName and addStudent

boolean containsName(String[] studentNamesArray, String studentName) {
  for (int i = 0; i < studentNamesArray.length; ++i) { // specialized while loop over all array elements
    if (studentName.equals(studentNamesArray[i])) { // use equals for String comparison! This will as well not match on "null"
      return true; // we found a match
    }
  }
  return false; // no match was found
}

And

void addStudent(String[] studentNamesArray, String studentName) {
  int i = 0; 
  while ((studentNamesArray[i] != null) && // this student entry is already filled by someone else
         (i < studentNamesArray.length)) { // we are still within the array bounds
    ++i;
  }
  if (i < studentNamesArray.length) { // is i still within the array bounds?
    studentNamesArray[i] = studentName; // add the student
  } else {
    // we have too many students. What to do now?
  }
}

There are several things not checked in this code:

• What if there are more students than the size of the array?
• What if studentName is null?

This approach to writing code is called Top-down approach and makes coding much easier, if you know the general program logic, but not yet the details.

Edit: The full code:

import java.util.Scanner;

public class Test {

  static boolean containsName(String[] studentNamesArray, String studentName) {
    for (int i = 0; i < studentNamesArray.length; ++i) { // specialized while loop over all array elements
      if (studentName.equals(studentNamesArray[i])) { // use equals for String comparison! This will as well not match on "null"
        return true; // we found a match
      }
    }
    return false; // no match was found
  }

  static void addStudent(String[] studentNamesArray, String studentName) {
    int i = 0;
    while ((studentNamesArray[i] != null) && // this student entry is already filled by someone else
            (i < studentNamesArray.length)) { // we are still within the array bounds
      ++i;
    }
    if (i < studentNamesArray.length) { // is i still within the array bounds?
      studentNamesArray[i] = studentName; // add the student
    } else {
      // we have too many students. What to do now?
    }
  }

  public static void main(String[] args) {
    final String[] studentNamesArray = new String[10];
    String studentName;

    final Scanner scanner = new Scanner(System.in);

    do {
      System.out.println("Please insert your name:");
      studentName = scanner.nextLine();
      if (studentName.length() > 0) {
        if (containsName(studentNamesArray, studentName) == false) {
          addStudent(studentNamesArray, studentName);
          System.out.println(studentName + " added.");
        } else {
          System.out.println(studentName + " was already in the list.");
        }
      }
    } while (studentName.length() > 0);

    for (int i = 0; i < studentNamesArray.length; ++i) {
      System.out.println("Student #" + i + ": " + studentNamesArray[i]);
    }
  }
}

Using sample input, I get the following:

Please insert your name:
Two
Two added.
Please insert your name:
Test
Test added.
Please insert your name:
Test
Test was already in the list.
Please insert your name:
test
test added.
Please insert your name:
test
test was already in the list.
Please insert your name:

Student #0: Two
Student #1: Test
Student #2: test
Student #3: null
Student #4: null
Student #5: null
Student #6: null
Student #7: null
Student #8: null
Student #9: null