1/*
2 * Copyright (C) 2008 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.collect;
18
19import static com.google.common.base.Preconditions.checkState;
20
21import com.google.common.annotations.GwtCompatible;
22
23/**
24 * Precondition checks useful in collection implementations.
25 */
26@GwtCompatible
27final class CollectPreconditions {
28
29  static void checkEntryNotNull(Object key, Object value) {
30    if (key == null) {
31      throw new NullPointerException("null key in entry: null=" + value);
32    } else if (value == null) {
33      throw new NullPointerException("null value in entry: " + key + "=null");
34    }
35  }
36
37  static int checkNonnegative(int value, String name) {
38    if (value < 0) {
39      throw new IllegalArgumentException(name + " cannot be negative but was: " + value);
40    }
41    return value;
42  }
43
44  /**
45   * Precondition tester for {@code Iterator.remove()} that throws an exception with a consistent
46   * error message.
47   */
48  static void checkRemove(boolean canRemove) {
49    checkState(canRemove, "no calls to next() since the last call to remove()");
50  }
51}
52