Update #0 - First Release

sources/main/java/com/google/common/collect/CollectPreconditions.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2008 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License 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.google.common.collect;
+
+import static com.google.common.base.Preconditions.checkState;
+
+import com.google.common.annotations.GwtCompatible;
+
+/**
+ * Precondition checks useful in collection implementations.
+ */
+@GwtCompatible
+final class CollectPreconditions {
+
+	static void checkEntryNotNull(Object key, Object value) {
+		if (key == null) {
+			throw new NullPointerException("null key in entry: null=" + value);
+		} else if (value == null) {
+			throw new NullPointerException("null value in entry: " + key + "=null");
+		}
+	}
+
+	static int checkNonnegative(int value, String name) {
+		if (value < 0) {
+			throw new IllegalArgumentException(name + " cannot be negative but was: " + value);
+		}
+		return value;
+	}
+
+	/**
+	 * Precondition tester for {@code Iterator.remove()} that throws an exception
+	 * with a consistent error message.
+	 */
+	static void checkRemove(boolean canRemove) {
+		checkState(canRemove, "no calls to next() since the last call to remove()");
+	}
+}