Tokens - Strings Java

Question

I have the following assignment that I succeeded, however the code is very inefficient, I would appreciate if someone could show me a more efficient way, perhaps with substring. the assignment:

/**
 * Separates a given string into tokens, which are the "words" that are
 * separated by one or more occurrences of the given separator character.
 * Returns the tokens as an array of String values.
 */
public static String[] tokenize (String str, char separator) {
    // Removes all the occurrences of the separator at the beginning and end of str
    String source = trim(str, separator);
    String[] tokens = new String[charRunCount (source,separator)+1];
    String tmp = ""; // a string in order to take a word, then run over this string
    int j = 0;
    int i = 0;
    while (i < tokens.length) {
        if ( source.charAt (j) != separator ) {
            do {
                tmp += source.charAt (j);
                if ( j >= source.length () - 1 ) {
                    break;
                }
                else { // so that we math the source length
                    j++;
                }
            } while (source.charAt (j) != separator); 
        }
        if ( source.charAt (j) == separator ) {
            j++;
            while (source.charAt (j) == separator) {
                j++;
            }
        }
        tokens[i] = tmp;// taking the token into place
        tmp = ""; //resetting the token so we can begin anew

        i++;
    }
    return tokens;
}

the cahrRunCount function:

    public static int charRunCount(String str, char c){
    char last = 0;
    int counter = 0;
    for (int i = 0; i < str.length(); i++) {
        // whenever a run starts.
        if (last != c && str.charAt(i) == c) {
            counter++;
        }
        last = str.charAt(i);
    }
    return counter;
}

I cannot use import or regex, thank you!

If your code works but needs improving, CodeReview might be a better place to post it. — jsheeran
– jsheeran, Commented Nov 5, 2018 at 15:54

greengreyblue · Accepted Answer · 2018-11-05 16:33:55Z

3

Use String.split method

String[] tokens = str.split(separator)


for(String token:tokens){
//your code goes here
}

Docs here

https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#split(java.lang.String)

edited Nov 5, 2018 at 16:33

answered Nov 5, 2018 at 15:52

greengreyblue

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1 Comment

Yuki1112 Over a year ago

how would you use it in a for loop for example? because separator is a char

Taher A. Ghaleb · Accepted Answer · 2018-11-06 00:36:56Z

1

If you want, you can use the split method of the String class (just like @Amidala Siva Kumar suggested), like this:

public static String[] tokenize (String str, char separator) {
    String[] tokens = str.split(separator);
    return tokens;
}

Or, if you want to do it using your own split, you may do it like this (an improvement to your code).

public static String[] tokenize (String str, char separator) {
    String sep = ""+separator;
    int max_size = str.length() - str.replace(sep, "").length() +1 ; // Calculate max array size
    String[] temp = new String[max_size];
    int start = 0, index = 0, exact_size = 0;
    int pos = str.indexOf(separator);
    while (pos>=start) {
        if (pos>start){
            temp[index++] = str.substring(start,pos).trim();
            exact_size++;
        }
        start = pos + 1;
        pos = str.indexOf(separator,start); 
    }
    String[] tokens = new String[exact_size];
    System.arraycopy(temp, 0, tokens, 0, exact_size); 
    return tokens;
}

Hope you find it useful.

edited Nov 6, 2018 at 0:36

answered Nov 5, 2018 at 17:27

Taher A. Ghaleb

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1 Comment

Yuki1112 Over a year ago

I wasn't aware of the split function, how would you implement it?

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