src/main/java/io/reactivex/internal/observers/DeferredScalarDisposable.java
public final void complete() {
        int state = get();
        if ((state & (FUSED_READY | FUSED_CONSUMED | TERMINATED | DISPOSED)) != 0) {
            return;
        }
        lazySet(TERMINATED);
        downstream.onComplete();
    }
public final void complete() {
        int state = get();
        if ((state & (FUSED_READY | FUSED_CONSUMED | TERMINATED | DISPOSED)) != 0) {
            return;
        }
        lazySet(TERMINATED);
        downstream.onComplete();
    }
Complete the target without any value.