### Question:
AppKey implements Comparable<Object> { public String toString() { return getCluster() + Constants.SEP + getUserName() + Constants.SEP + getAppId(); } @JsonCreator  AppKey(@JsonProperty("cluster") String cluster, @JsonProperty("userName") String userName,
      @JsonProperty("appId") String appId); String getCluster(); String getUserName(); String getAppId(); String toString(); @Override int compareTo(Object other); @Override boolean equals(Object other); @Override int hashCode();  }### Answer:
@Test public void testToString() { AppKey key = new AppKey("c1@local", "auser", "app"); String expected = "c1@local" + Constants.SEP + "auser" + Constants.SEP + "app"; assertEquals(expected, key.toString()); }