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Reactive event streams for JavaFX

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package org.reactfx;

import java.util.Objects;

/**
 * See {@link EventStream#distinct()}
 */
class DistinctStream extends EventStreamBase {
    static final Object NONE = new Object();
    private final EventStream input;
    private Object previous = NONE;

    public DistinctStream(EventStream input) {
        this.input = input;
    }

    @Override
    protected Subscription observeInputs() {
        return input.subscribe(value -> {
            Object prevToCompare = previous;
            previous = value;
            if (!Objects.equals(value, prevToCompare)) {
                emit(value);
            }
        });
    }
}