As the execution time is consumed mostly by waiting for <abbr title="Input and Output">I/O</abbr> operations, they call them "I/O bound" operations.

It's called "asynchronous" because the computer / program doesn't have to be "synchronized" with the slow task, waiting for the exact moment that the task finishes, while doing nothing, to be able to take the task result and continue the work.

            case 2:
                md4.update(ntHash);
                md4.digest(dest, offset, 16);
                break;
            case 3:
            case 4:
            case 5:
                synchronized ( this ) {
                    if ( this.clientChallenge == null ) {
                        this.clientChallenge = new byte[8];
                        tc.getConfig().getRandom().nextBytes(this.clientChallenge);

  public void testOrderingUnmodifiable() {
    Multimap<String, Integer> multimap = initializeMultimap5();
    assertOrderingReadOnly(Multimaps.unmodifiableMultimap(multimap));
  }

  @J2ktIncompatible // Synchronized
  public void testOrderingSynchronized() {
    Multimap<String, Integer> multimap = initializeMultimap5();
    assertOrderingReadOnly(synchronizedMultimap(multimap));
  }

  @J2ktIncompatible

import java.util.concurrent.atomic.AtomicReference;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Serializes execution of tasks, somewhat like an "asynchronous {@code synchronized} block." Each
 * {@linkplain #submit enqueued} callable will not be submitted to its associated executor until the
 * previous callable has returned -- and, if the previous callable was an {@link AsyncCallable}, not

    }
    static void writeUTime( long t, byte[] dst, int dstIndex ) {
        if( t == 0L || t == 0xFFFFFFFFFFFFFFFFL ) {
            writeInt4( 0xFFFFFFFF, dst, dstIndex );
            return;
        }
        synchronized( TZ ) {
            if( TZ.inDaylightTime( new Date() )) {
                // in DST
                if( TZ.inDaylightTime( new Date( t ))) {
                    // t also in DST so no correction

    public org.apache.maven.api.plugin.descriptor.MojoDescriptor getMojoDescriptorV4() {
        if (mojoDescriptorV4 == null) {
            synchronized (this) {
                if (mojoDescriptorV4 == null) {
                    mojoDescriptorV4 = org.apache.maven.api.plugin.descriptor.MojoDescriptor.newBuilder()
                            .goal(goal)

        // length == 0 should not happen
        return getUNCPath().length() <= 1;
    }


    /**
     * @throws MalformedURLException
     * 
     */
    private synchronized void canonicalizePath () {
        char[] in = this.url.getPath().toCharArray();
        char[] out = new char[in.length];
        int length = in.length, prefixLen = 0, state = 0;

        /*

    protected String reportActiveExternalHost;

    protected boolean useEPSVwithIPv4;

    protected Boolean isImplicit;

    protected String trustManager;

    @Override
    public synchronized void init() {
        if (ftpAuthenticationHolder != null) {
            return;
        }

        super.init();

                      multimap.put(entry.getKey(), entry.getValue());
                    }
                    return multimap;
                  }
                })
            .named("synchronized ArrayListMultimap")
            .withFeatures(
                MapFeature.ALLOWS_NULL_KEYS,
                MapFeature.ALLOWS_NULL_VALUES,
                MapFeature.ALLOWS_ANY_NULL_QUERIES,

    protected int numberOfReplicas = 1;

    protected int idPrefixLength = 445;

    protected FesenClient getClient() {
        if (!fesenClient.connected()) {
            synchronized (fesenClient) {
                if (!fesenClient.connected()) {
                    fesenClient.connect();
                }
            }
        }
        return fesenClient;
    }