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Showing content from https://firebase.google.com/docs/reference/android/com/google/firebase/database/MutableData below:

MutableData | Firebase SDKs for Android

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public class MutableData

Instances of this class encapsulate the data and priority at a location. It is used in transactions, and it is intended to be inspected and then updated to the desired data at that location. Note that changes made to a child MutableData instance will be visible to the parent and vice versa.

public long getChildrenCount()

The number of immediate children at this location

public @Nullable Object getPriority()

Gets the current priority at this location. The possible return types are:

• Double
• String

Note that null is allowed

The priority at this location as a native type or null if no priority was set

public @Nullable Object getValue()

getValue() returns the data contained in this instance as native types. The possible types returned are:

• Boolean
• Long
• Double
• String
• Map<String, Object>
• List<Object>

This list is recursive; the possible types for

in the above list is given by the same list. These types correspond to the types available in JSON.

The data contained in this instance as native types, or null if there is no data at this location.

public @Nullable T <T> getValue(@NonNull GenericTypeIndicator<T> t)

Due to the way that Java implements generics, it takes an extra step to get back a properly-typed Collection. So, in the case where you want a java.util.List of Message instances, you will need to do something like the following:

    GenericTypeIndicator<List<Message>> t =
        new GenericTypeIndicator<List<Message>>() {};
    List<Message> messages = mutableData.getValue(t);

It is important to use a subclass of

. See

for more details

A properly typed collection, populated with the data from this instance, or null if there is no data at this location.

public @Nullable T <T> getValue(@NonNull Class<T> valueType)

This method is used to marshall the data contained in this instance into a class of your choosing. The class must fit 2 simple constraints:

1. The class must have a default constructor that takes no arguments
2. The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized

An example class might look like:

    class Message {
        private String author;
        private String text;

        private Message() {}

        public Message(String author, String text) {
            this.author = author;
            this.text = text;
        }

        public String getAuthor() {
            return author;
        }

        public String getText() {
            return text;
        }
    }


    // Later
    Message m = mutableData.getValue(Message.class);

The type to return. Implicitly defined from the class passed in

The class into which this data in this instance should be marshalled

An instance of the class passed in, populated with the data from this instance, or null if there is no data at this location.

public boolean hasChild(@NonNull String path)

True if data exists at the given path, otherwise false

public boolean hasChildren()

True if the data at this location has children, false otherwise

public void setValue(@Nullable Object value)

Set the data at this location to the given value. The native types accepted by this method for the value correspond to the JSON types:

• Boolean
• Long
• Double
• Map<String, Object>
• List<Object>

In addition, you can set instances of your own class into this location, provided they satisfy the following constraints:

1. The class must have a default constructor that takes no arguments
2. The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized

Generic collections of objects that satisfy the above constraints are also permitted, i.e.

, as well as null values.

Note that this overrides the priority, which must be set separately.

The value to set at this location or null to delete the existing data

public final T <T extends Object> DatabaseKt.getValue(@NonNull MutableData receiver)

Returns the content of the MutableData converted to a POJO.

Supports generics like List<> or Map<>. Use @JvmSuppressWildcards to force the compiler to use the type T, and not ? extends T.

Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies. Java is a registered trademark of Oracle and/or its affiliates.

Last updated 2025-07-21 UTC.

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