CODEWITHSUNDEEP
javaarraylistindexof
user2981089
user2981089

Reputation: 21

Arraylist indexOf always returns -1 Java

I'm doing a project for class in which you have to make a Hall of Fame and be able to add/remove/search/edit different kinds of bands. Right now, I'm having trouble with searching the index for a specific band because it always returns -1 and I'm not sure why.

Here is my code:

public class HallofFame
{
    public static ArrayList<Band> hallOfFame = new ArrayList<Band>();
    public static Scanner scan = new Scanner(System.in);
    public static void main(String[]args){
        int a = 0;
        while(a == 0){
            System.out.println("What would you like to do?");
            System.out.println("");
            System.out.println("1. Add");
            System.out.println("2. Remove");
            System.out.println("3. Edit");
            System.out.println("4. Clear");
            System.out.println("5. Search");
            System.out.println("6. Quit");
            System.out.println("");
            String choice = scan.nextLine();
            if(choice.equals ("1")){
                add();
            }
            else if(choice.equals ("2")){
                remove();
            }
            else if(choice.equals ("3")){
                edit();
            }
            else if(choice.equals ("4")){
                clear();
            }
            else if(choice.equals ("5")){
                search();
            }
            else if(choice.equals ("6")){
                quit();
                break;
            }
        }
    }

    public static void add(){
        Scanner booblean = new Scanner(System.in);
        System.out.println("What is the name of the band you would like to add?");
        String name = scan.nextLine();
        System.out.println("What kind of genre is this band?");
        String genre = scan.nextLine();
        System.out.println("How many members are in the band?");
        int numMem = scan.nextInt();
        System.out.println("How many songs does this band have?");
        int numSongs = scan.nextInt();
        System.out.println("How many albums does this band have?");
        int numAlbs = scan.nextInt();
        System.out.println("Is this band currently active?");
        String yesno = booblean.nextLine();
        boolean isActive = false;
        if(yesno.equalsIgnoreCase ("yes")){
            isActive = true;
        }
        Band b1 = new Band(name, genre, numMem, numSongs, numAlbs, isActive);
        hallOfFame.add(b1);
        System.out.println("");
        System.out.println("The band " + name + " has been added to the database.");
        System.out.println("");
    }

    public static void remove(){

    }

    public static void edit(){
        System.out.println("What band info do you want to edit?");
        String searchband = scan.nextLine();
    }

    public static void clear(){
        hallOfFame.clear();
    }

    public static void search(){
        System.out.println("What band name are you searching for?");
        String searchband = scan.nextLine();
        int retval = hallOfFame.indexOf(searchband);
        System.out.println("The band " + searchband + " is at index: " + retval);
    }

    public static void quit(){
        System.exit(0);
    }
}

The search method is the one I'm having trouble with.

Upvotes: 1

Views: 410

Answers (4)

Hoa Nguyen
Hoa Nguyen

Reputation: 178

One way is you need make a Band's constructor with param is name. Then you can search the Object "Band" in ArrayList hallOfFame

Upvotes: 1

Tien Nguyen
Tien Nguyen

Reputation: 4358

You should override both equals and hashCode to make it work perfectly.

Overriding equals and hashCode in Java

Upvotes: 1

josephus
josephus

Reputation: 8304

Alternatively, you can override the equals method of Band so that indexOf would actually work.

I'd imagine it would read something like this:

@Override

public boolean equals(Object o) {

  return ((Band) o).name==this.name;

}

Upvotes: 2

musical_coder
musical_coder

Reputation: 3896

The problem is that hallOfFame contains Band objects, but you're searching hallOfFame for a String. Instead, iterate through hallOfFame and compare band names to the inputted string.

Upvotes: 3

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