Copyright (c) 2016-present, RxJava Contributors.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is
distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
the License for the specific language governing permissions and limitations under the License.
/**
 * Copyright (c) 2016-present, RxJava Contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
 * the License for the specific language governing permissions and limitations under the License.
 */

package io.reactivex.subjects;

import io.reactivex.*;
import io.reactivex.annotations.*;

Represents an Observer and an Observable at the same time, allowing multicasting events from a single source to multiple child Observers. 
 All methods except the Observer.onSubscribe(Disposable), Observer.onNext(Object), Observer.onError(Throwable) and Observer.onComplete() are thread-safe. Use toSerialized() to make these methods thread-safe as well. 
Type parameters:
<T> – the item value type/**
 * Represents an {@link Observer} and an {@link Observable} at the same time, allowing
 * multicasting events from a single source to multiple child {@code Observer}s.
 * <p>
 * All methods except the {@link #onSubscribe(io.reactivex.disposables.Disposable)}, {@link #onNext(Object)},
 * {@link #onError(Throwable)} and {@link #onComplete()} are thread-safe.
 * Use {@link #toSerialized()} to make these methods thread-safe as well.
 *
 * @param <T> the item value type
 */
public abstract class Subject<T> extends Observable<T> implements Observer<T> {
    
Returns true if the subject has any Observers.
The method is thread-safe.
Returns:
true if the subject has any Observers/**
     * Returns true if the subject has any Observers.
     * <p>The method is thread-safe.
     * @return true if the subject has any Observers
     */
    public abstract boolean hasObservers();

    
Returns true if the subject has reached a terminal state through an error event.
The method is thread-safe.
See Also:
getThrowable()
hasComplete()
Returns:
true if the subject has reached a terminal state through an error event/**
     * Returns true if the subject has reached a terminal state through an error event.
     * <p>The method is thread-safe.
     * @return true if the subject has reached a terminal state through an error event
     * @see #getThrowable()
     * @see #hasComplete()
     */
    public abstract boolean hasThrowable();

    
Returns true if the subject has reached a terminal state through a complete event.
The method is thread-safe.
See Also:
hasThrowable()
Returns:
true if the subject has reached a terminal state through a complete event/**
     * Returns true if the subject has reached a terminal state through a complete event.
     * <p>The method is thread-safe.
     * @return true if the subject has reached a terminal state through a complete event
     * @see #hasThrowable()
     */
    public abstract boolean hasComplete();

    
Returns the error that caused the Subject to terminate or null if the Subject
hasn't terminated yet.
The method is thread-safe.
Returns:
the error that caused the Subject to terminate or null if the Subject
hasn't terminated yet/**
     * Returns the error that caused the Subject to terminate or null if the Subject
     * hasn't terminated yet.
     * <p>The method is thread-safe.
     * @return the error that caused the Subject to terminate or null if the Subject
     * hasn't terminated yet
     */
    @Nullable
    public abstract Throwable getThrowable();

    
Wraps this Subject and serializes the calls to the onSubscribe, onNext, onError and
onComplete methods, making them thread-safe.
The method is thread-safe.
Returns:
the wrapped and serialized subject/**
     * Wraps this Subject and serializes the calls to the onSubscribe, onNext, onError and
     * onComplete methods, making them thread-safe.
     * <p>The method is thread-safe.
     * @return the wrapped and serialized subject
     */
    @NonNull
    public final Subject<T> toSerialized() {
        if (this instanceof SerializedSubject) {
            return this;
        }
        return new SerializedSubject<T>(this);
    }
}