Java, Simplified check if int array contains int
JavaArraysIntContainsJava Problem Overview
Basically my mate has been saying that I could make my code shorter by using a different way of checking if an int array contains an int, although he won't tell me what it is :P.
Current:
public boolean contains(final int[] array, final int key) {
for (final int i : array) {
if (i == key) {
return true;
}
}
return false;
}
Have also tried this, although it always returns false for some reason.
public boolean contains(final int[] array, final int key) {
return Arrays.asList(array).contains(key);
}
Could anyone help me out?
Thank you.
Java Solutions
Solution 1 - Java
You could simply use ArrayUtils.contains
from Apache Commons Lang library.
public boolean contains(final int[] array, final int key) {
return ArrayUtils.contains(array, key);
}
Solution 2 - Java
Here is Java 8 solution
public static boolean contains(final int[] arr, final int key) {
return Arrays.stream(arr).anyMatch(i -> i == key);
}
Solution 3 - Java
It's because Arrays.asList(array)
returns List<int[]>
. The array
argument is treated as one value you want to wrap (you get a list of arrays of ints), not as vararg.
Note that it does work with object types (not primitives):
public boolean contains(final String[] array, final String key) {
return Arrays.asList(array).contains(key);
}
or even:
public <T> boolean contains(final T[] array, final T key) {
return Arrays.asList(array).contains(key);
}
But you cannot have List<int>
and autoboxing is not working here.
Solution 4 - Java
Guava offers additional methods for primitive types. Among them a contains method which takes the same arguments as yours.
public boolean contains(final int[] array, final int key) {
return Ints.contains(array, key);
}
You might as well statically import the guava version.
See [Guava Primitives Explained][1]
[1]: http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained "Guava Primitives Explained"
Solution 5 - Java
A different way:
public boolean contains(final int[] array, final int key) {
Arrays.sort(array);
return Arrays.binarySearch(array, key) >= 0;
}
This modifies the passed-in array. You would have the option to copy the array and work on the original array i.e. int[] sorted = array.clone();
But this is just an example of short code. The runtime is O(NlogN)
while your way is O(N)
Solution 6 - Java
I know it's super late, but try Integer[]
instead of int[]
.
Solution 7 - Java
1.one-off uses
List<T> list=Arrays.asList(...)
list.contains(...)
2.use HashSet for performance consideration if you use more than once.
Set <T>set =new HashSet<T>(Arrays.asList(...));
set.contains(...)
Solution 8 - Java
You can convert your primitive int array into an arraylist of Integers using below Java 8 code,
List<Integer> arrayElementsList = Arrays.stream(yourArray).boxed().collect(Collectors.toList());
And then use contains()
method to check if the list contains a particular element,
boolean containsElement = arrayElementsList.contains(key);
Solution 9 - Java
Try this:
public static void arrayContains(){
int myArray[]={2,2,5,4,8};
int length=myArray.length;
int toFind = 5;
boolean found = false;
for(int i = 0; i < length; i++) {
if(myArray[i]==toFind) {
found=true;
}
}
System.out.println(myArray.length);
System.out.println(found);
}
Solution 10 - Java
You can use java.util.Arrays
class to transform the array T[?]
in a List<T>
object with methods like contains
:
Arrays.asList(int[] array).contains(int key);
Solution 11 - Java
this worked in java 8
public static boolean contains(final int[] array, final int key)
{
return Arrays.stream(array).anyMatch(n->n==key);
}
Solution 12 - Java
private static void solutions() {
int[] A = { 1, 5, 10, 20, 40, 80 };
int[] B = { 6, 7, 20, 80, 100 };
int[] C = { 3, 4, 15, 20, 30, 70, 80, 120 };
List<Integer> aList = Arrays.stream(A).boxed().collect(Collectors.toList());
List<Integer> cList = Arrays.stream(C).boxed().collect(Collectors.toList());
String s = "";
for (Integer a : C) {
if (aList.contains(a) && cList.contains(a)) {
s = s.concat(String.valueOf(a)).concat("->");
}
}
}
Solution 13 - Java
Java 9+
public boolean contains(final int[] array, final int key) {
return List.of(array).contains(key);
}
Solution 14 - Java
Depending on how large your array of int will be, you will get much better performance if you use collections and .contains
rather than iterating over the array one element at a time:
import static org.junit.Assert.assertTrue;
import java.util.HashSet;
import org.junit.Before;
import org.junit.Test;
public class IntLookupTest {
int numberOfInts = 500000;
int toFind = 200000;
int[] array;
HashSet<Integer> intSet;
@Before
public void initializeArrayAndSet() {
array = new int[numberOfInts];
intSet = new HashSet<Integer>();
for(int i = 0; i < numberOfInts; i++) {
array[i] = i;
intSet.add(i);
}
}
@Test
public void lookupUsingCollections() {
assertTrue(intSet.contains(toFind));
}
@Test
public void iterateArray() {
assertTrue(contains(array, toFind));
}
public boolean contains(final int[] array, final int key) {
for (final int i : array) {
if (i == key) {
return true;
}
}
return false;
}
}
Solution 15 - Java
Try Integer.parseInt()
to do this.....
public boolean chkInt(final int[] array){
int key = false;
for (Integer i : array){
try{
Integer.parseInt(i);
key = true;
return key;
}catch(NumberFormatException ex){
key = false;
return key;
}
}
}