NotEmptyIterableVerifier.java

// =================================================================================================
// Copyright 2011 Twitter, Inc.
// -------------------------------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this work except in compliance with the License.
// You may obtain a copy of the License in the LICENSE file, or at:
//
//  http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// =================================================================================================

package com.twitter.common.args.constraints;

import java.lang.annotation.Annotation;

import com.google.common.collect.Iterables;

import com.twitter.common.args.Verifier;
import com.twitter.common.args.VerifierFor;

import static com.google.common.base.Preconditions.checkArgument;

/**
 * Verifies that an iterable is not empty.
 *
 * @author William Farner
 */
@VerifierFor(NotEmpty.class)
public class NotEmptyIterableVerifier implements Verifier<Iterable<?>> {
  @Override
  public void verify(Iterable<?> value, Annotation annotation) {
    checkArgument(!Iterables.isEmpty(value), "Value must not be empty.");
  }

  @Override
  public String toString(Class<? extends Iterable<?>> argType, Annotation annotation) {
    return "must have at least 1 item";
  }
}