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 17 package com.google.common.collect; 18 19 import static com.google.common.base.Preconditions.checkState; 20 21 import com.google.common.annotations.GwtCompatible; 22 23 /** 24 * Precondition checks useful in collection implementations. 25 */ 26 @GwtCompatible 27 final class CollectPreconditions { 28 checkEntryNotNull(Object key, Object value)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 checkNonnegative(int value, String name)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 */ checkRemove(boolean canRemove)48 static void checkRemove(boolean canRemove) { 49 checkState(canRemove, "no calls to next() since the last call to remove()"); 50 } 51 } 52