### Question:
PeerId implements Copiable<PeerId>, Serializable, Checksum { @Override public long checksum() { if (this.checksum == 0) { this.checksum = CrcUtil.crc64(AsciiStringUtil.unsafeEncode(toString())); } return this.checksum; } PeerId();  PeerId(final Endpoint endpoint, final int idx);  PeerId(final String ip, final int port);  PeerId(final String ip, final int port, final int idx);  PeerId(final Endpoint endpoint, final int idx, final int priority);  PeerId(final String ip, final int port, final int idx, final int priority); @Override long checksum(); static PeerId emptyPeer(); @Override PeerId copy(); static PeerId parsePeer(final String s); Endpoint getEndpoint(); String getIp(); int getPort(); int getIdx(); int getPriority(); void setPriority(int priority); boolean isEmpty(); @Override String toString(); boolean parse(final String s); boolean isPriorityNotElected(); boolean isPriorityDisabled(); @Override int hashCode(); @Override boolean equals(final Object obj); static final PeerId ANY_PEER; }### Answer:
@Test public void testChecksum() { PeerId peer = new PeerId("192.168.1.1", 8081, 1); long c = peer.checksum(); assertTrue(c != 0); assertEquals(c, peer.checksum()); }