4 ways to search array in Java Read more: http://javarevisited.blogspot.com/2012/11/4-ways-to-search-object-in-java-array-example.html

searchArray.java

/*1) Searching Array by converting Array to ArrayList in Java
ArrayList in Java has a convenient method called contains() which returns true if object passed to it are inside ArrayList. by converting an array into ArrayList in Java we can easily use this option for searching any element in Java array.

2) Search Java array by converting Array to HashSet
Just like we can leverage ArrayList's contains method we can also use HashSet contains() method which has O(1) response time for search. So if you need constant search time to find an element in array, consider converting your Array into HashSet in Java. see the code section for complete example of searching elements in Java array using HashSet's contains() method.

3) Searching Java Array using Arrays.binarySearch()
Binary Search is another faster way of searching elements in Java array but it requires array to be sorted while earlier examples of finding elements on Array can be used with both sorted and unsorted array. java.util.Arrays class provides both sort() and binarySearch() for first sorting an array and than performing binary search on it. Arrays.binarySearch() method returns >=0 if it finds elements in Array. see code section for full code example of binarySearch in Java array.

4) Finding element in Java array using foreach loop
This is plain, old, brute force way of searching elements on array in Java or any other programming language like C or C++. You iterate through array comparing each elements to input and returning true once you have matched. this is a completely linear operation and if your array is large and input is at rear end it can take long time to search array. O(n) operations are also not preferred.
*/

import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class SearchTest {

    public static void main(String args[]) {

        //searching element on unsorted Java array
        //searching java array using ArrayList
        List<Integer> array = Arrays.asList(1, 3, 5, 2, 4);
        if (array.contains(3)) {
            System.out.println("Element found inside Java array using" +
                                 "ArrayList contains() method");
        };

        Set<Integer> arraySet = new HashSet<Integer>(array);

        if (arraySet.contains(3)) {
            System.out.println("Element found on Java array using" +
                                 "HashSet contains method");
        };
      
        //searching element on sorted Java array
        //unsorted String array
        String[] cities = new String[]{"Washington", "London", "Paris", "NewYork"};
      
        //sorting array in java
        Arrays.sort(cities);
      
        //searching on sorted array in java using Arrays binarySearch() method
        if(Arrays.binarySearch(cities, "Paris") >=0 ){
            System.out.println("Element found on sorted String Java" +
                                  "array using binary search");
        }
      
        //plain old for loop for searching elements in Java array
        String input = "London";
        for(String city: cities){
            if(city.equals(input)){
               System.out.println("Found elements in Java array using for loop");
            }
        }

    }
}

Output
Element found inside Java array using  ArrayList contains() method
Element found on Java array using HashSet contains method
Element found on sorted String Java array using binary search
Found elements in Java array using for loop


Read more: http://javarevisited.blogspot.com/2012/11/4-ways-to-search-object-in-java-array-example.html#ixzz2jPAjiogo