How to find index of STRING array in Java from a given value?

Question

I wanted to know if there's a native method in array for Java to get the index of the table for a given value ?

Let's say my table contains these strings :

public static final String[] TYPES = {
        "Sedan",
        "Compact",
        "Roadster",
        "Minivan",
        "SUV",
        "Convertible",
        "Cargo",
        "Others"
    };

Let's say the user has to enter the type of car and that then in the background the program takes that string and get's it's position in the array.

So if the person enters : Sedan It should take the position 0 and store's it in the object of Cars created by my program ...

possible duplicate of [Where is Java's Array indexOf?](http://stackoverflow.com/questions/4962361/where-is-javas-array-indexof) — Ciro Santilli OurBigBook.com, Mar 03 '15 at 07:23

score 204 · Answer 1 · edited Nov 22 '18 at 15:30

204

Type in:

Arrays.asList(TYPES).indexOf("Sedan");

edited Nov 22 '18 at 15:30

Devealte

219
3
19

answered Apr 18 '14 at 19:30

6

This uses the Arrays class to convert the TYPES array to a List object. The List class has a method(.indexOf) which will return the index of the passed in object (in this case a String). Nice solution if you don't mind creating the List out of the array. +1 – Craig B Nov 06 '14 at 05:55
1

The array is converted to a list which costs cpu and battery on mobile but it will perform correctly. – Gary Davies Oct 12 '16 at 08:49
3

Great, but you should comment that must import java.util.Arrays – Adexe Rivera Oct 22 '18 at 11:20
2

@GaryDavies If you care about Object/List creation in java, you are in the wrong language ... – kaiser Oct 22 '19 at 06:30

score 31 · Accepted Answer · answered Apr 18 '14 at 19:26

31

String carName = // insert code here
int index = -1;
for (int i=0;i<TYPES.length;i++) {
    if (TYPES[i].equals(carName)) {
        index = i;
        break;
    }
}

After this index is the array index of your car, or -1 if it doesn't exist.

answered Apr 18 '14 at 19:26

Anubian Noob

13,426
6
53
75

score 13 · Answer 3 · answered Apr 18 '14 at 19:28

13

for (int i = 0; i < Types.length; i++) {
    if(TYPES[i].equals(userString)){
        return i;
    }
}
return -1;//not found

You can do this too:

return Arrays.asList(Types).indexOf(userSTring);

answered Apr 18 '14 at 19:28

Mohsen Kamrani

7,177
5
42
66

score 12 · Answer 4 · edited Apr 23 '17 at 06:32

12

I had an array of all English words. My array has unique items. But using…

Arrays.asList(TYPES).indexOf(myString);

…always gave me indexOutOfBoundException.

So, I tried:

Arrays.asList(TYPES).lastIndexOf(myString);

And, it worked. If your arrays don't have same item twice, you can use:

Arrays.asList(TYPES).lastIndexOf(myString);

edited Apr 23 '17 at 06:32

Tzar

5,132
4
23
57

answered Apr 23 '17 at 03:30

suhid

121
1
3

score 8 · Answer 5 · answered Aug 27 '15 at 03:30

8

try this instead

org.apache.commons.lang.ArrayUtils.indexOf(array, value);

answered Aug 27 '15 at 03:30

Wayne

81
1
4

score 6 · Answer 6 · answered Apr 18 '14 at 19:34

6

Use Arrays class to do this

Arrays.sort(TYPES);
int index = Arrays.binarySearch(TYPES, "Sedan");

answered Apr 18 '14 at 19:34

Arjit

3,290
1
17
18

1

Can't `TYPES` not be sorted because it is `final`? – The Guy with The Hat Apr 18 '14 at 19:57
6

The OP wants to know the index of the string in the list in its original order. Once you sort it you will likely be returning a different index from where it was originally. – Craig B Nov 06 '14 at 05:41
1

Also regarding "final". Standard java arrays are mutable regardless of whether they are declared final. Final just means that the TYPES variable cannot have another object assigned to it. Guava has some immutable collections which might be worth looking into if you are interested. – Craig B Nov 06 '14 at 06:15

score 5 · Answer 7 · answered Nov 06 '17 at 08:30

5

No built-in method. But you can implement one easily:

public static int getIndexOf(String[] strings, String item) {
    for (int i = 0; i < strings.length; i++) {
        if (item.equals(strings[i])) return i;
    }
    return -1;
}

answered Nov 06 '17 at 08:30

Raphael C

2,296
1
22
22

score 2 · Answer 8 · answered Oct 19 '16 at 05:47

2

There is no native indexof method in java arrays.You will need to write your own method for this.

answered Oct 19 '16 at 05:47

abhishek58g

145
4

score 1 · Answer 9 · answered Apr 18 '14 at 19:34

An easy way would be to iterate over the items in the array in a loop.

for (var i = 0; i < arrayLength; i++) {
 // (string) Compare the given string with myArray[i]
 // if it matches store/save i and exit the loop.
}

There would definitely be better ways but for small number of items this should be blazing fast. Btw this is javascript but same method should work in almost every programming language.

score 0 · Answer 10 · answered Apr 18 '14 at 19:29

Try this Function :

public int indexOfArray(String input){
     for(int i=0;i<TYPES,length();i++)
       {
         if(TYPES[i].equals(input))
         {
          return i ;
         }
        }
      return -1     // if the text not found the function return -1
      }

Gary Davies · Answer 11 · 2016-10-12T10:40:18.687

Testable mockable interafce

public interface IArrayUtility<T> {

    int find(T[] list, T item);

}

implementation

public class ArrayUtility<T> implements IArrayUtility<T> {

    @Override
    public int find(T[] array, T search) {
        if(array == null || array.length == 0 || search == null) {
            return -1;
        }

        int position = 0;

        for(T item : array) {

            if(item.equals(search)) {
                return position;
            } else {
                ++position;
            }
        }

        return -1;
    }

}

Test

@Test
public void testArrayUtilityFindForExistentItemReturnsPosition() {
    // Arrange
    String search = "bus";
    String[] array = {"car", search, "motorbike"};

    // Act
    int position = arrayUtility.find(array, search);

    // Assert
    Assert.assertEquals(position, 1);
}

score 0 · Answer 12 · edited Feb 08 '17 at 11:53

0

Use this as a method with x being any number initially. The string y being passed in by console and v is the array to search!

public static int getIndex(int x, String y, String[]v){
    for(int m = 0; m < v.length; m++){
        if (v[m].equalsIgnoreCase(y)){
            x = m;
        }
    }
    return x;
}

edited Feb 08 '17 at 11:53

CroMagnon

1,218
7
20
32

answered Feb 08 '17 at 10:40

mitchell Williamson

1

score 0 · Answer 13 · answered Dec 20 '19 at 13:26

Refactoring the above methods and showing with the use:

private String[] languages = {"pt", "en", "es"};
private Integer indexOf(String[] arr, String str){
   for (int i = 0; i < arr.length; i++)
      if(arr[i].equals(str)) return i;
   return -1;
}
indexOf(languages, "en")

How to find index of STRING array in Java from a given value?

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