| /* |
| * Copyright (C) 2011 The Android Open Source Project |
| * |
| * 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.android.internal.util; |
| |
| /** |
| * Simple static methods to be called at the start of your own methods to verify |
| * correct arguments and state. |
| */ |
| public class Preconditions { |
| |
| /** |
| * Ensures that an object reference passed as a parameter to the calling |
| * method is not null. |
| * |
| * @param reference an object reference |
| * @return the non-null reference that was validated |
| * @throws NullPointerException if {@code reference} is null |
| */ |
| public static <T> T checkNotNull(T reference) { |
| if (reference == null) { |
| throw new NullPointerException(); |
| } |
| return reference; |
| } |
| |
| /** |
| * Ensures that an object reference passed as a parameter to the calling |
| * method is not null. |
| * |
| * @param reference an object reference |
| * @param errorMessage the exception message to use if the check fails; will |
| * be converted to a string using {@link String#valueOf(Object)} |
| * @return the non-null reference that was validated |
| * @throws NullPointerException if {@code reference} is null |
| */ |
| public static <T> T checkNotNull(T reference, Object errorMessage) { |
| if (reference == null) { |
| throw new NullPointerException(String.valueOf(errorMessage)); |
| } |
| return reference; |
| } |
| |
| /** |
| * Ensures the truth of an expression involving the state of the calling |
| * instance, but not involving any parameters to the calling method. |
| * |
| * @param expression a boolean expression |
| * @throws IllegalStateException if {@code expression} is false |
| */ |
| public static void checkState(boolean expression) { |
| if (!expression) { |
| throw new IllegalStateException(); |
| } |
| } |
| |
| /** |
| * Check the requested flags, throwing if any requested flags are outside |
| * the allowed set. |
| */ |
| public static void checkFlagsArgument(int requestedFlags, int allowedFlags) { |
| if ((requestedFlags & allowedFlags) != requestedFlags) { |
| throw new IllegalArgumentException("Requested flags 0x" |
| + Integer.toHexString(requestedFlags) + ", but only 0x" |
| + Integer.toHexString(allowedFlags) + " are allowed"); |
| } |
| } |
| } |