decompose a string into array of int

What is the shortest and most efficient way to decompose a string array into an array of int's if the string looks like:

4 1 4 2 3
5 1 4 2 -1 6

The way I have it now is to use 开发者_StackOverflow中文版String split method and iterate the String array into int's.. Is there a better way than this?

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That's fine - I'd just call split(" ") and then use Integer.parseInt() on the resulting elements.

If you could potentially have more than one space between the ints, you'll need something like split("\\s+") for it to work properly.

If that's what you're doing, I don't think there's a better way!

EDIT: Perhaps I should qualify the term better - I mean that for all practical purposes, unless you're really hitting performance critical issues, I'd stick with this method since it's clean and easy to understand what's going on!

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Using split() consumes more space [and time], as new String objects are created, but it is far more elegant [and simple] then any other way.

unless performance is very critical, I'd stick with this way.

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Algorithm 3times faster than the split method! :)

Just for the fun of it I have made an algorithm that is far faster than the split method. Maybe nothing you should use as I would say split is cleaner and cleaner is far more important than speed. Also the Donald Knuth quote of premature optimizations are the root cause of all evil.

Output

1189ms // My algorithm first loop
3305ms // Split algorithm runtime first loop
1173ms // My algorithm second loop
3305ms // Split algorithm second loop

The code

import java.util.ArrayList;

class FarmorsOptimized {

@SuppressWarnings({ "rawtypes", "unchecked" })
private static ArrayList getFarmors(String s) {
    ArrayList intArr = new ArrayList();
    int stopvalue = s.length() ;
    for (int i = 0; i < stopvalue;) {
        int negativ = 0;
        if (s.charAt(i) == '-') {
            negativ = 1;
        }
        intArr.add(Integer.parseInt(s.substring(i, i+1+negativ)));
        i+=2+negativ;
    }
    return intArr;
}

@SuppressWarnings({ "rawtypes", "unchecked" })
private static ArrayList getSplits(String s) {
    ArrayList intArr = new ArrayList();
    for(String str : s.split(" ")){
        intArr.add(Integer.parseInt(str));
    }
    return intArr;
}

public static void main(String[] args) {
    String s = "1 2 4 -6 7 1 2 4 -6 7 1 2 4 -6 7 1 2 4 -6 7 1 2 4 -6 7 1 2 4 -6 7 1 2 4 -6 7";
    int times = 1000000;
    //Just to init everything
    for (int i = 0; i < times; i++) {
        getFarmors(s);
        getSplits(s);
    }
    long starttime = System.currentTimeMillis();
    for (int i = 0; i < times; i++) {
        getFarmors(s);
    }
    System.out.println(System.currentTimeMillis() - starttime);
    starttime = System.currentTimeMillis();
    for (int i = 0; i < times; i++) {
        getSplits(s);
    }
    System.out.println(System.currentTimeMillis() - starttime);
    starttime = System.currentTimeMillis();
    for (int i = 0; i < times; i++) {
        getFarmors(s);
    }
    System.out.println(System.currentTimeMillis() - starttime);
    starttime = System.currentTimeMillis();
    for (int i = 0; i < times; i++) {
        getSplits(s);
    }
    System.out.println(System.currentTimeMillis() - starttime);
}

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Answer to comment discussion. This answer works for all ints. It's significantly faster than the split.

1295ms my
2193ms split
1155ms my
1889ms split

code

import java.util.ArrayList;

class FarmorsOptimized {

public static void main(String[] args) {
    String s = "32324 -324 873249 -8544876 -74093 -3243274 4325 643286 92325 -21376218 -213 2132531 2314 1 2";
    int times = 1000000;
    long starttime = System.currentTimeMillis();
    for (int i = 0; i < times; i++) {
        getFarmors(s);
    }
    System.out.println(System.currentTimeMillis() - starttime);
    starttime = System.currentTimeMillis();
    for (int i = 0; i < times; i++) {
        getSplits(s);
    }
    System.out.println(System.currentTimeMillis() - starttime);
    starttime = System.currentTimeMillis();
    for (int i = 0; i < times; i++) {
        getFarmors(s);
    }
    System.out.println(System.currentTimeMillis() - starttime);
    starttime = System.currentTimeMillis();
    for (int i = 0; i < times; i++) {
        getSplits(s);
    }
    System.out.println(System.currentTimeMillis() - starttime);
}

@SuppressWarnings({ "rawtypes", "unchecked" })
private static ArrayList getFarmors(String s) {
    ArrayList intArr = new ArrayList();
    int stopvalue = s.length();
    for (int i = 0; i < stopvalue;) {
        int j = 0;
        while (true) {
            if ((i + j) == stopvalue || s.charAt(i + j) == ' ') {
                break;
            }
            j++;
        }
        intArr.add(Integer.parseInt(s.substring(i, i + j)));
        i += j + 1;
    }
    return intArr;
}

@SuppressWarnings({ "rawtypes", "unchecked" })
private static ArrayList getSplits(String s) {
    ArrayList intArr = new ArrayList();
    String[] strArr = s.split(" ");
    for(int i = 0; i < strArr.length ; i++){
        intArr.add(Integer.parseInt(strArr[i]));
    }
    return intArr;
}

}