Are there other ways to get a List from a String other than splitting it?

Question

There is a string which is a separated string : item_1|item_2|item_3 , in this example the separating symbol is |.

My boss does not like the split method to get the different parts of the string: he thinks there is risk about it, but he is not very sure what is the risk. So are there other ways to get a List from a separated String?

Answer 1

import java.util.ArrayList;
import java.util.List;

public class SplitUsingAnotherMethodBecauseBossLikesWastingEveryonesTime {

    public static void main(String[] args) {
        System.out.println(split("Why would anyone want to write their own String split function in Java?", ' '));
        System.out.println(split("The|Split|Method|Is|Way|More|Flexible||", '|'));
    }

    private static List<String> split(String input, char delimiter) {
        List<String> result = new ArrayList<>();
        int idx = 0;
        int next;

        do {
            next = input.indexOf(delimiter, idx);

            if (next > -1) {
                result.add(input.substring(idx, next));
                idx = next + 1;
            }
        } while(next > -1);

        result.add(input.substring(idx));

        return result;
    }
}

Outputs...

[Why, would, anyone, want, to, write, their, own, String, split, function, in, Java?]
[The, Split, Method, Is, Way, More, Flexible, , ]

Answer 2

You can just iterate over all the chars in the string and then use substring() to select the different sub strings:

public static List<String> split(String input, char delimiter) {
    List<String> output = new LinkedList<>();
    int lastIndex = 0;
    boolean doubleQuote = false;
    boolean singleQuoteFound = false;
    for (int i = 0, current, last = 0, length = input.length(); i < length; i++) {
        current = input.charAt(i);
        if (last != '\\') {
            if (current == '"') {
                doubleQuote = !doubleQuote;
            } else if (current == '\'') {
                singleQuoteFound = !singleQuoteFound;
            } else if (current == delimiter && !doubleQuote && !singleQuoteFound) {
                output.add(input.substring(lastIndex, i));
                lastIndex = i + 1;
            }
        }
        last = current;
    }
    output.add(input.substring(lastIndex));
    return output;
}

This is a very crude approach, but from my testing it should take care of escaped delimiters, delimiters in single ' and/or double " -quotes.

Can be called like this:

List<String> splitted = split("Hello|World|"No|split|here"|\|Was escaped|'Some|test'", '|');

Prints:

[Hello, World, "No|split|here", \|Was escaped, 'Some|test']

Answer 3

When we use split string, it internally creates Patterns object which overhead but that is only true for before Java 7 version only, In Java 7/8 it use index of since java 7 it wont have any overhead of the regular expression engine.However, if you do pass a more complex expression, it reverts to compiling a new pattern and here the behavior should be the same as that on Java 6 you can use pre compiled pattern and split the string.

public class MyClass {
static Pattern pattern = Pattern.compile("\\|");
public static void main(String[] args) {
    String str = "item_1|item_2|item_3";
    Stream<String> streamsName = pattern.splitAsStream(str);
    streamsName.forEach(System.out::println);
}

}