Trying to find if a java list object has an element STRING or INT?

Question

I am trying to find if a list contains a string. I have a list object as follows:

Please note this is just example code, to illustrate my point/question!

import java.util.List;

public class FilterByList {

    private String actionHero;
    private String actionHero2;
    private String move;
    private int number;
    private String actionHero3;

    public FilterByList(String actionHero, String actionHero2, String move, int number, String actionHero3) {
        this.actionHero = actionHero;
        this.actionHero2 = actionHero2;
        this.move = move;
        this.number = number;
        this.actionHero3 = actionHero3;
    }

    public String getActionHero() {
        return actionHero;
    }

    public void setActionHero(String actionHero) {
        this.actionHero = actionHero;
    }

    public String getActionHero2() {
        return actionHero2;
    }

    public void setActionHero2(String actionHero2) {
        this.actionHero2 = actionHero2;
    }

    public String getMove() {
        return move;
    }

    public void setMove(String move) {
        this.move = move;
    }

    public int getNumber() {
        return number;
    }

    public void setNumber(int number) {
        this.number = number;
    }

    public String getActionHero3() {
        return actionHero3;
    }

    public void setActionHero3(String actionHero3) {
        this.actionHero3 = actionHero3;
    }
}

And then:

public static void main(String[] args) {

    List<FilterByList> myList = Collections.singletonList(
    new FilterByList("superman", "antman", "ACTION", 123, "batman"));

    System.out.println(myList);
    if (myList.contains("batman")) {
        System.out.println("found it!");
    } else {
        System.out.println("************************* Did not find anything!!1");
    }
}

It does NOT find batman in the list object. So what is printed is the follows:

[com.company.FilterByList@7577b641]
************************* Did not find anything!!1

Any idea how I can:

a) print the contents of the list?

b) find an element in the list with as little code as possible?

Would appreciate your help. Please use my code context to answer as it will give me more pointers.

It is usually considered not best practice to store multiple different types in the same collection. Why do you need to do this? — Tim Biegeleisen
– Tim Biegeleisen, Commented Dec 28, 2018 at 13:57
Add toString method to FilterByList and run myList.forEach(System.out::println); — Bartosz Wardziński
– Bartosz Wardziński, Commented Dec 28, 2018 at 13:59
myList contains only one FilterByList object, and this object doesn't equal to "batmat". — Danila Zharenkov
– Danila Zharenkov, Commented Dec 28, 2018 at 14:00
@DanilaZharenkov - Sure. Any way to see what is inside that FilterByList object? — Saffik
– Saffik, Commented Dec 28, 2018 at 14:02

Bartosz Wardziński · Accepted Answer · 2018-12-28 14:15:58Z

1

You run contains on List<FilterByList> and that list doesn't have String batman It has instance of FilterByList, that one of members is field of type string and value 'batman'

Based on your code. You create instance of object FilterByList and you try to compare that object with String

Line

if (myList.contains("batman")) {

Those object are different types, that is the reason, why it is not found

To check if there is batman you can use Stream API

boolean d = myList.stream().map(FilterByList::getActionHero3).anyMatch(hero3 -> hero3.equals("batman"));

edited Dec 28, 2018 at 14:15

answered Dec 28, 2018 at 14:02

Bartosz Wardziński

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3 Comments

Saffik Over a year ago

Can you give me an example (in code) based on my code please, sorry. Just trying to understand more...

Saffik Over a year ago

Ok i see what you are saying. Is there a way to find it?

Saffik Over a year ago

Wow. Streams is a nice thing to do! I will upvote but the other guy answered first so can award him. I really appreciate your help and telling me about stream api. I'll definitely read up more on it. :)

Danila Zharenkov · Accepted Answer · 2018-12-28 14:16:25Z

1

Add to your FilterByList class containsHero(String hero) where you compare hero with each of 3 heroes. You don't need to store this single object in List. Just use it.

  FilterByList f = new FilterByList("superman", "antman", "ACTION", 123, "batman");
  if (f.containsHero("batman")) {
      System.out.println("found it!");
  } else {
      System.out.println("************************* Did not find anything!!1");
  }

P.S. imho all the things you are trying to do looks very strange...

answered Dec 28, 2018 at 14:16

Danila Zharenkov

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Comments

Joakim Danielson · Accepted Answer · 2018-12-28 14:46:48Z

I added a new method to the class for searching

public boolean containsHero(String hero) {
    return actionHero.equals(hero) ||  actionHero2.equals(hero) ||  actionHero3.equals(hero);
}

And then used it with streams like this

if (myList.stream().anyMatch(f -> f.containsHero("batman"))) {
    System.out.println("found it!");
}

To get a readable output of your class you can override the toString() method, here is one example

@Override
public String toString() {
    StringBuilder builder = new StringBuilder();
    builder.append(actionHero);
    builder.append(", ");
    builder.append(actionHero2);
    builder.append(", ");

    builder.append(actionHero3);
    builder.append(": ");

    builder.append(move);
    builder.append(": ");

    builder.append(number);

    return builder.toString();
}

Doing System.out.println(myList);will then output

[superman, antman, batman: ACTION: 123]

Aleksandr Podkutin · Accepted Answer · 2018-12-28 14:40:46Z

0

You can put into the list two different types of objects, e.g. String and Integer if you will omit the generic type, and implicitly it will be List<Object> myList = new ArrayList<Object>(); for example:

List myList = new ArrayList();
myList.add("superman");
myList.add("antman");
myList.add("ACTION");
myList.add(123);
myList.add("batman");

System.out.println(myList);
if (myList.contains("batman")) {
    System.out.println("found it!");
} else {
    System.out.println("************************* Did not find anything!!1");
}

But it's not a good way to use collections. For sure, it depends of your particular task, but I'd like to advice to use different collections with different types.

If you want to achieve exactly what you're asking about, you can use Stream API like this:

List<FilterByList> myList = Collections.singletonList(
new FilterByList("superman", "antman", "ACTION", 123, "batman"));

System.out.println(myList);
if (myList.stream().map(FilterByList::getActionHero3).allMatch("batman"::equals)) {
    System.out.println("found it!");
} else {
    System.out.println("************************* Did not find anything!!1");
}

anyMatch method is more preferable to use, if there will be more than one element in the collection:

(myList.stream().map(FilterByList::getActionHero3).anyMatch("batman"::equals))

edited Dec 28, 2018 at 14:40

answered Dec 28, 2018 at 14:04

Aleksandr Podkutin

2,6101 gold badge24 silver badges32 bronze badges

3 Comments

Saffik Over a year ago

Thanks for this. I needed to use List<FilterByList> myList, I updated my question..

Bartosz Wardziński Over a year ago

I think it should be anyMatch instead allMatch

Aleksandr Podkutin Over a year ago

@wardziniak For the example which @Saffik was provided allMatch is more strict. But of course if it will be more that one element in the collection it will be better to use anyMatch. Thanks

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