Interface Predicate

hbase-common/src/test/java/org/apache/hadoop/hbase/Waiter.java:85–93

A predicate 'closure' used by the Waiter#waitFor(Configuration, long, Predicate) and Waiter#waitFor(Configuration, long, Predicate) and Waiter#waitFor(Configuration, long, long, boolean, Predicate) methods.

   * {@link Waiter#waitFor(Configuration, long, long, boolean, Predicate)} methods.
   */
  @InterfaceAudience.Private
  public interface Predicate<E extends Exception> {
    /**
     * Perform a predicate evaluation.
     * @return the boolean result of the evaluation.
     * @throws E thrown if the predicate evaluation could not evaluate.
     */
    boolean evaluate() throws E;
  }

  /**
   * A mixin interface, can be used with {@link Waiter} to explain failed state.