How do I determine whether an array contains a particular value in Java?

Question

I have a String[] with values like so:

public static final String[] VALUES = new String[] {\"AB\",\"BC\",\"CD\",\"AE\"};

Given

Answer 1

Try this:

ArrayList<Integer> arrlist = new ArrayList<Integer>(8);

// use add() method to add elements in the list
arrlist.add(20);
arrlist.add(25);
arrlist.add(10);
arrlist.add(15);

boolean retval = arrlist.contains(10);
if (retval == true) {
    System.out.println("10 is contained in the list");
}
else {
    System.out.println("10 is not contained in the list");
}

Answer 2

You can use ArrayUtils.contains from Apache Commons Lang

public static boolean contains(Object[] array, Object objectToFind)

Note that this method returns false if the passed array is null.

There are also methods available for primitive arrays of all kinds.

Example:

String[] fieldsToInclude = { "id", "name", "location" };

if ( ArrayUtils.contains( fieldsToInclude, "id" ) ) {
    // Do some stuff.
}

Answer 3

Actually, if you use HashSet<String> as Tom Hawtin proposed you don't need to worry about sorting, and your speed is the same as with binary search on a presorted array, probably even faster.

It all depends on how your code is set up, obviously, but from where I stand, the order would be:

On an unsorted array:

1. HashSet
2. asList
3. sort & binary

On a sorted array:

1. HashSet
2. Binary
3. asList

So either way, HashSet for the win.

Answer 4

You can check it by two methods

A)By converting the array into string and then check the required string by .contains method

 String a=Arrays.toString(VALUES);
    System.out.println(a.contains("AB"));
    System.out.println(a.contains("BC"));
    System.out.println(a.contains("CD"));
    System.out.println(a.contains("AE"));

B)this is a more efficent method

 Scanner s=new Scanner(System.in);


   String u=s.next();
   boolean d=true;
    for(int i=0;i<VAL.length;i++)
    {
        if(VAL[i].equals(u)==d)
            System.out.println(VAL[i] +" "+u+VAL[i].equals(u));  

    }

Answer 5

As I'm dealing with low level Java using primitive types byte and byte[], the best so far I got is from bytes-java https://github.com/patrickfav/bytes-java seems a fine piece of work