Java Simplified check if int array contains int

Question

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

User · Accepted Answer

Here is Java 8 solution  public static boolean contains final int   arr  final int key        return Arrays stream arr  anyMatch i - gt  i    key

User · Answer

A different way      public boolean contains final int   array  final int key           Arrays sort array          return Arrays binarySearch array  key   gt   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

User · Answer

1 one-off uses   List lt T gt  list Arrays asList      list contains        2 use HashSet for performance consideration if you use more than once   Set  lt T gt set  new HashSet lt T gt  Arrays asList        set contains

User · Answer

I know it s super late  but try Integer   instead of int

User · Answer

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

User · Answer

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 lt Integer gt  intSet    Before public void initializeArrayAndSet         array   new int numberOfInts       intSet   new HashSet lt Integer gt         for int i   0  i  lt  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

User · Answer

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

User · Answer

It s because Arrays asList array  return List lt int   gt   array argument is treated as one value you want to wrap  you get 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  lt T gt   boolean contains final T   array  final T key        return Arrays asList array  contains key       But you cannot have List lt int gt  and autoboxing is not working here

User · Answer

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

User · Answer

You can use java util Arrays class to transform the array T    in a List lt T gt  object with methods like contains   Arrays asList int   array  contains int key

User · Answer

You can convert your primitive int array into an arraylist of Integers using below Java 8 code   List lt Integer gt  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

User · Answer

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  lt  length  i              if myArray i   toFind                found true                       System out println myArray length       System out println found

User · Answer

this worked in java 8  public static boolean contains final int   array  final int key    return Arrays stream array  anyMatch n- gt n  key

User · Answer

Solution  1  Since the original question only wants a simplified solution  and not a faster one   here is a one-line solution   public boolean contains int   array  int key        return Arrays toString array  matches              key                    Explanation  Javadoc of Arrays toString   states the result is enclosed in square brackets and adjacent elements are separated by the characters       a comma followed by a space   So we can count on this  First we convert array to a string  and then we check if key is contained in this string  Of course we cannot accept  sub-numbers   e g   1234  contains  23    so we have to look for patterns where the key is preceded with an opening bracket or a space  and followed by a closing bracket or a comma   Note  The used regexp pattern also handles negative numbers properly  whose string representation starts with a minus sign    Solution  2  This solution is already posted but it contains mistakes  so I post the correct solution   public boolean contains int   array  int key        Arrays sort array       return Arrays binarySearch array  key   gt   0      Also this solution has a side effect  it modifies the array  sorts it

[java] Java, Simplified check if int array contains int

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