Java List.contains(Object with field value equal to x)

Streams

If you are using Java 8, perhaps you could try something like this:

public boolean containsName(final List<MyObject> list, final String name){
    return list.stream().filter(o -> o.getName().equals(name)).findFirst().isPresent();
}

Or alternatively, you could try something like this:

public boolean containsName(final List<MyObject> list, final String name){
    return list.stream().map(MyObject::getName).filter(name::equals).findFirst().isPresent();
}

This method will return true if the List<MyObject> contains a MyObject with the name name. If you want to perform an operation on each of the MyObjects that getName().equals(name), then you could try something like this:

public void perform(final List<MyObject> list, final String name){
    list.stream().filter(o -> o.getName().equals(name)).forEach(
            o -> {
                //...
            }
    );
}

Where o represents a MyObject instance.

Alternatively, as the comments suggest (Thanks MK10), you could use the Stream#anyMatch method:

public boolean containsName(final List<MyObject> list, final String name){
    return list.stream().anyMatch(o -> o.getName().equals(name));
}

You have two choices.

1. The first choice, which is preferable, is to override the `equals()` method in your Object class.

Let's say, for example, you have this Object class:

public class MyObject {
    private String name;
    private String location;
    //getters and setters
}

Now let's say you only care about the MyObject's name, that it should be unique so if two `MyObject`s have the same name they should be considered equal. In that case, you would want to override the `equals()` method (and also the `hashcode()` method) so that it compares the names to determine equality.

Once you've done this, you can check to see if a Collection contains a MyObject with the name "foo" by like so:

MyObject object = new MyObject();
object.setName("foo");
collection.contains(object);

However, this might not be an option for you if:

• You are using both the name and location to check for equality, but you only want to check if a Collection has any `MyObject`s with a certain location. In this case, you've already overridden `equals()`.
• `MyObject` is part of an API that you don't have liberty to change.

If either of these are the case, you'll want option 2:

2. Write your own utility method:

public static boolean containsLocation(Collection<MyObject> c, String location) {
    for(MyObject o : c) {
        if(o != null && o.getLocation.equals(location)) {
            return true;
        }
    }
    return false;
}

Alternatively, you could extend ArrayList (or some other collection) and then add your own method to it:

public boolean containsLocation(String location) {
    for(MyObject o : this) {
        if(o != null && o.getLocation.equals(location)) {
                return true;
            }
        }
        return false;
    }

Unfortunately there's not a better way around it.

This is how to do it using Java 8+ :

boolean isJohnAlive = list.stream().anyMatch(o -> o.getName().equals("John"));