从Java中的（字符串）数组中删除Null元素

Question

Hey guys, I'm new to Java (well, 3/4 of a year spent on it).

So I don't know much about it, I can do basic things, but the advanced concepts have not been explained to me, and there is so much to learn! So please go a little but easy on me...

Ok, so I have this project where I need to read lines of text from a file into an array but only those which meet specific conditions. Now, I read the lines into the array, and then skip out on all of those which don't meet the criteria. I use a for loop for this. This is fine, but then when I print out my array (required) null values crop up all over the place where I skipped out on the words.

How would I remove the null elements specifically? I have tried looking everywhere, but the explanations have gone way over my head!

Here is the code that I have to deal with the arrays specifically: (scanf is the scanner, created a few lines ago):

//create string array and re-open file
    scanf = new Scanner(new File ("3letterWords.txt"));//re-open file
    String words [] = new String [countLines];//word array
    String read = "";//to read file

    int consonant=0;//count consonants
    int vowel=0;//count vowels

    //scan words into array
    for (int i=0; i<countLines; i++)
    {
        read=scanf.nextLine();

        if (read.length()!=0)//skip blank lines
        {    
            //add vowels
            if (read.charAt(0)=='a'||read.charAt(0)=='e'||read.charAt(0)=='i'||read.charAt(0)=='o'||read.charAt(0)=='u')
            {
                if (read.charAt(2)=='a'||read.charAt(2)=='e'||read.charAt(2)=='i'||read.charAt(2)=='o'||read.charAt(2)=='u')
                {
                    words[i]=read;
                    vowel++;
                }
            }
            //add consonants
            if (read.charAt(0)!='a'&&read.charAt(0)!='e'&&read.charAt(0)!='i'&&read.charAt(0)!='o'&&read.charAt(0)!='u')
            {
                if (read.charAt(2)!='a'&&read.charAt(2)!='e'&&read.charAt(2)!='i'&&read.charAt(2)!='o'&&read.charAt(2)!='u')
                {
                    words[i]=read;
                    consonant++;
                }
            }

        }//end if

        //break out of loop when reached EOF
        if (scanf.hasNext()==false)
            break;

    }//end for

    //print data
    System.out.println("There are "+vowel+" vowel words\nThere are "+consonant+" consonant words\nList of words: ");

   for (int i=0; i<words.length; i++)
       System.out.println(words[i]);

Thanks so much for any help received!

Answer 1

Just have a different counter for the words array and increment it only when you add a word:

int count = 0;

for (int i=0; i<countLines; i++) {
  ...
  // in place of: words[i] = read;
  words[count++] = read;
  ...
}

When printing the words, just loop from 0 to count .

---

Also, here's a simpler way of checking for a vowel/consonant. Instead of:

if (read.charAt(0)=='a'||read.charAt(0)=='e'||read.charAt(0)=='i'||read.charAt(0)=='o'||read.charAt(0)=='u')

you can do:

if ("aeiou".indexOf(read.charAt(0)) > -1)

Update: Say read.charAt(0) is some character x . The above line says look for that character in the string "aeiou" . indexOf returns the position of the character if found or -1 otherwise. So anything > -1 means that x was one of the characters in "aeiou" , in other words, x is a vowel.

Answer 2

public static String[] removeElements(String[] allElements) {
    String[] _localAllElements = new String[allElements.length];

    for(int i = 0; i < allElements.length; i++)
        if(allElements[i] != null)
            _localAllElements[i] = allElements[i];

    return _localAllElements;
}