With this example we are going to demonstrate how to search elements in a ArrayList. In short, to search elements in a ArrayList you should:
- Create a new ArrayList.
- Populate the arrayList with elements, using
add(E e)API method of ArrayList. - Check if an element exists in the arrayList, with
contains(Object element)API method of ArrayList. The method returns true if the element exists in the arrayList and false otherwise. - Invoke
indexOf(Object element)API method of ArrayList, to get the index of the first occurance of the specified element in ArrayList or -1 if the specific element is not found. - To get the index of the last occurance of this element in the arrayList we can use
lastIndexOf(Object element)method.
Let’s take a look at the code snippet that follows:
package com.javacodegeeks.snippets.core;
import java.util.ArrayList;
public class SearchElementsInArrayList {
public static void main(String[] args) {
// Create an ArrayList and populate it with elements
ArrayList arrayList = new ArrayList();
arrayList.add("element_1");
arrayList.add("element_2");
arrayList.add("element_3");
arrayList.add("element_1");
/*
boolean contains(Object element) operation returns true
if the ArrayList contains the specified object, false otherwise.
*/
boolean found = arrayList.contains("element_2");
System.out.println("Found element_2 : " + found);
/*
int indexOf(Object element) operation returns the index of the
first occurance of the specified element in ArrayList or -1 if
the specific element is not found. To get the index of the last
occurance of the specified element in ArrayList use the
int lastIndexOf(Object element) operation instead.
*/
int index = arrayList.indexOf("element_3");
System.out.println("Found element_3 : " + (index == -1?false:true) + ", in position : " + index);
int lastIndex = arrayList.lastIndexOf("element_1");
System.out.println("Found element_1 : " + (lastIndex == -1?false:true) + ", in position : " + lastIndex);
}
}
Output:
Found element_2 : true
Found element_3 : true, in position : 2
Found element_1 : true, in position : 3
This was an example of how to search elements in a ArrayList in Java.
