Given an array of Strings, how to find out the index of a particular String?

Question

I have,

String[] directions = {"North", "South", "West", "East"};

Not, I have a String s which is any one of those 4 String literals.

How do I get the index of s in directions?

You want the index. Try to search the `String` API for methods that might have a close name :). — Tunaki, Sep 29 '15 at 21:28
As a side rec, in this situation I'd use an enum, not Strings since this would restrict `s` to one of the for choices and nothing else. Also enums have a method for just this problem, `ordinal()`, although the API states that you would not likely need to use it. — Hovercraft Full Of Eels, Sep 29 '15 at 21:29
@HovercraftFullOfEels Can you show how it can be done using enums please? — Pretorious, Sep 29 '15 at 21:42

score 1 · Answer 1 · answered Sep 29 '15 at 21:45

A possible enum

public enum Direction {
    NORTH("North"), SOUTH("South"), EAST("East"), WEST("West");

    private String text;
    private Direction(String text) {
        this.text = text;
    }

    public String getText() {
        return text;
    }
}

public class TestDirection {
    public static void main(String[] args) {
        System.out.printf("%10s: %-4s%n", "Direction", "Ordinal");
        for (Direction dir : Direction.values()) {
            System.out.printf("%10s: %-4d%n", dir.getText(), dir.ordinal());
        }
    }
}

Which prints out:

 Direction: Ordinal
     North: 0   
     South: 1   
      East: 2   
      West: 3

but again, the devil is in the details. As the enum API for this method states:

Returns the ordinal of this enumeration constant (its position in its enum declaration, where the initial constant is assigned an ordinal of zero). Most programmers will have no use for this method. It is designed for use by sophisticated enum-based data structures, such as EnumSet and EnumMap.

score 1 · Answer 2 · answered Sep 29 '15 at 21:47

1

You can achieve this using a for loop as well..

int i, index;
for i = 0; i < directions.lenght()-1; i++{
    if(s.equals(directions[i]){
        index = i;
        break;
    }
}

answered Sep 29 '15 at 21:47

IvnBam

127
1
12

score 1 · Answer 3 · edited Jun 20 '17 at 12:23

1

Try this simple snippet:

String[] directions = {"North", "South", "West", "East"};

int directionIndex = Arrays.asList(directions).indexOf("West");

This will give you the index of any string within the array or returns -1 if it is absent.

edited Jun 20 '17 at 12:23

René Hoffmann

2,766
2
20
43

answered Jun 20 '17 at 11:50

Sathishkumar J

81
1
3

score 0 · Answer 4 · edited May 23 '17 at 12:14

0

You can for example use

java.util.Arrays.asList(directions).indexOf(s)

A more general question with several excellent answers can be found here. The above solution is one of the answers listed there.

edited May 23 '17 at 12:14

Community

1
1

answered Sep 29 '15 at 21:31

jurgispods

745
8
19

Thanks, buddy. How can I do the same using enums? – Pretorious Sep 29 '15 at 21:42
Are you looking for something like this? http://stackoverflow.com/a/15436799/2429404 – jurgispods Sep 29 '15 at 21:53

Given an array of Strings, how to find out the index of a particular String?

4 Answers4