how to get index of an element from bean type array list

Question

I want to get indexOf a first name from ArrayList.

Here is my bean class

public class BeanClass {
static String firstname;
String lastname;
int rollno;

public BeanClass(String firstname, String lastname, int rollno) {
    super();
    this.firstname = firstname;
    this.lastname = lastname;
    this.rollno = rollno;
}

and here is Main Activity

public class MainClass {

    static ArrayList<BeanClass>arraylist=new ArrayList<>();
    static String firstname[]={"kshitij","ravi","prakash","sunil"};
    staticString lastname[]={"singh","sharma","verma","tiwari"};
    staticint rollno[]={1,2,3,4};

    public static void main(String[] args) {

        for (int i = 0; i < firstname.length; i++) {
            BeanClass bean=new BeanClass(firstname[i],lastname[i],rollno[i]);
            arraylist.add(bean);
        }
         System.out.println(arraylist.indexOf("kshitij"));
    }
}

To do it the way you want, the ArrayList should have String as generic argument. You'll have to build you own function that iterates over the list, checking object by object if firstname is the one you passed as argument. — Nadir
– Nadir, Commented Mar 10, 2016 at 11:55

Vipin Jain · Accepted Answer · 2016-03-10 12:10:22Z

2

if you want to get index of following name you want to declare a variable

int index = 0;

and replace this line System.out.println(arraylist.indexOf("kshitij")); with this code

for (BeanClass bean: arraylist) {
    if (bean.firstname.equals("kshitij")) {           
        System.out.println("Index is " + index);
        break;
    }
    index++
}

its return index of your first name where it store. i assume index start from 0

edited Mar 10, 2016 at 12:10

answered Mar 10, 2016 at 12:04

Vipin Jain

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4 Comments

Pragnani Kinnera Over a year ago

You need to break, when you find the match

Vipin Jain Over a year ago

yes we can break but it's print index when the condition is true otherwise is skip to print it

Pragnani Kinnera Over a year ago

yes we can break but it's print index when the condition is true otherwise is skip to print it, Your statement doesn't make anysense..

Vipin Jain Over a year ago

its get index only when its condition true (bean.firstname.equals("kshitij")) else its not print index

Community · Accepted Answer · 2017-05-23 12:15:54Z

1

As mentioned here:Java ArrayList IndexOf - Finding Object Index

You should build your own equals method to be able to use indexOf. Also, you will need to pass an object of BeanClass to indexOf

public boolean equals(Object o) {
    if(!(o instanceof BeanClass)) return false;
    BeanClass other = (BeanClass) o;
    return (this.firstname == other.firstname && this.lastname == other.lastname );
}

edited May 23, 2017 at 12:15

CommunityBot

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answered Mar 10, 2016 at 12:02

AlexW

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Comments

Nikolas · Accepted Answer · 2016-03-10 12:09:46Z

1

Note that your ArrayList contains BeanClass. It's value is not "kshitij", but one of variable of your BeanClass.

You have to declare an index variable, loop ArrayList through and find your index out:

int index = 0; // Index variable
for (BeanClass bean: arraylist) {
    if (bean.firstname.equals("kshitij")) {
        System.out.println(index);
        break;
    } 
    index++;
}

Output:

By the way, in the BeanClass your variable firstname should be not static, or all of instances will have the firstname same is then searching it by a firstname loses a sence.

So redefine your BeanClass to:

public class BeanClass {
   String firstname;
   String lastname;
   int rollno;

   // ...
}

edited Mar 10, 2016 at 12:09

answered Mar 10, 2016 at 11:58

Nikolas

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3 Comments

Pragnani Kinnera Over a year ago

You need to break, when you find the match

Nikolas Over a year ago

Right, no need to loop more. Thanks for a hint.

Jiri Tousek Over a year ago

Also, OP is looking for index, not the value.

Austin · Accepted Answer · 2016-03-11 18:15:21Z

1

You can use an IntStream in Java 8 as follows:

IntStream.range(0, list.size())
    .filter(i -> arrayList.get(i).firstname.equals("kshiij"))
    .findFirst()
    .getAsInt();

Remember, getAsInt throws a NoSuchElementException if a matching element is not contained in the list. Don't forget to catch it.

edited Mar 11, 2016 at 18:15

answered Mar 10, 2016 at 12:10

Austin

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