如何使用迭代器测试字符串是否以元音开头

Question

I have written a program using an iterator for the first time. I have an array list of strings and I have printed them using the hasNext and next method. I am now trying to go backwards using the previous method and while doing so I am suppose to check each element and if it starts with a vowel I nedd to delete it from the list. Here is the piece of code that I am having trouble with.

while (iterator.hasPrevious())
      {
         String s = iterator.previous();
         if (s.startsWith("a"))
         {
            iterator.remove();
         }   
         System.out.print(" "+ s);
      }

Any help would be greatly appreciated!

Answer 1

String vowels = "aeiou";
String testString = ... // Iterator String 
if (vowels.indexOf(Character.toLowerCase(testString.charAt(0))) != -1) {
    ... // Start char is vowel
}

Answer 2

To check whether a String starts with a vowel, you can use regular expressions.

For instance:

String[] input = {"abc", "def", "ghi"};
for (String s: input) {
    System.out.printf("\"%s\" starts with a vowel? %b%n", s, s.matches("(?i)^[aeiouy].*$"));
}

Output

"abc" starts with a vowel? true
"def" starts with a vowel? false
"ghi" starts with a vowel? false

In your case...

The method startsWith only takes a literal, so it's not what you want.

Instead, you could use a constant Pattern in your class, such as:

static final Pattern STARTS_WITH_VOWEL = Pattern.compile("^[aeiouy]", Pattern.CASE_INSENSITIVE);

Then in your loop, you could use:

if (STARTS_WITH_VOWEL.matcher(s).find()) {
    ...
}

Answer 3

A readable way to do it would be to have a list of all the vowels

Collection<Character> vowels = new HasSet<~>();
vowels.add('a');
vowels.add('e');
vowels.add('i');
vowels.add('o');
vowels.add('u');

Then what you could do is

if (vowels.conatins(Character.toLowerCase(s)))
{
    iterator.remove();
}

Answer 4

just change the if to include more conditions

if (s.startsWith("a") || if (s.startsWith("A"))...)