Java Strings empty string handling

Question

I have a Java code that should print nothing if no-element string is passed.Currently,my method is passing all tests but the one with no-element string.It gives me error.Code is below.Any suggestions are welcome.

public static void printLetters(String text)
{

System.out.print(text.charAt(0));

for(int i=1;i<text.length();i++)
{
    System.out.print("-" + text.charAt(i));
}

System.out.println();
}

Answer 1

My guess is your exception pops up on your line

System.out.print(text.charAt(0));

If you pass an empty string the code will try to access a char at 0. In the empty string there is no 0th char.

A check like this might suit you:

public static void printLetters(String text)
{
    if (text != null && text.length() != 0)
    {
        System.out.print(text.charAt(0));

        for(int i=1;i<text.length();i++)
        {
            System.out.print("-" + text.charAt(i));
        }
    }
    System.out.println();
}

Answer 2

It should be giving you giving you NullPointerException if you pass null because you are de-referencing text before checking if it is null or not and de-referencing null results in NPE.

if(text != null){
return;
}

For empty String test you can do the following

if(text.isEmpty()){
System.out.println(text);
}

Answer 3

You can simply add an if statement to check if the text variable is null, if so return.

Also you can remove the first System.out.print(text.charAt(0)); and just change so the for loop starts at i = 0

public static void printLetters(String text)
{
    if (text == null)
    {
        return;
    }

    for(int i = 0; i < text.length(); i++)
    {
        System.out.print(text.charAt(i) + ",");
    }

    System.out.println();
}

Answer 4

The reason why you have this problem is because if you have a string which has a null pointer the charAt(0) will automatically throw a NullPointerException. Try to evaluate first if the string has null pointet, if it's not then you can go ahead and use charAt(0) and the other operations.