1 /* 2 * Copyright (C) 2012 The Android Open Source Project 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 package com.android.tradefed.util; 17 18 /** 19 * A class with utility functions to help with dealing with <code>null</code> 20 */ 21 public class NullUtil { 22 /** 23 * Counts <code>null</code> objects in the passed set 24 */ 25 public static int countNulls(Object... objs) { 26 int count = 0; 27 for (Object obj : objs) { 28 if (obj == null) count++; 29 } 30 return count; 31 } 32 33 /** 34 * Counts non-<code>null</code> objects in the passed set 35 */ 36 public static int countNonNulls(Object... objs) { 37 int count = 0; 38 for (Object obj : objs) { 39 if (obj != null) count++; 40 } 41 return count; 42 } 43 44 /** 45 * Checks if all objects are null. Uses short-circuit logic, so may be more efficient than 46 * {@link #countNonNulls(Object...)} for sets of many objects. 47 * 48 * @return <code>false</code> if any passed objects are non-null. <code>true</code> otherwise. 49 * In particular, returns true of no objects are passed. 50 */ 51 public static boolean allNull(Object... objs) { 52 for (Object obj : objs) { 53 if (obj != null) return false; 54 } 55 return true; 56 } 57 58 /** 59 * Checks if exactly one object is non-null. Uses short-circuit logic, so may be more efficient 60 * than {@link #countNonNulls(Object...)} for sets of many objects. 61 * 62 * @return <code>true</code> if there is exactly one non-<code>null</code> object in the list. 63 * <code>false</code> otherwise. 64 */ 65 public static boolean singleNonNull(Object... objs) { 66 int nonNullCount = 0; 67 for (Object obj : objs) { 68 if (obj != null) nonNullCount++; 69 if (nonNullCount > 1) return false; 70 } 71 return nonNullCount == 1; 72 } 73 74 /** 75 * Check if every object is null, or every object is non-null. Uses short-circuit logic, so may 76 * be more efficient than {@link #countNulls(Object...)} and {@link #countNonNulls(Object...)} 77 * for sets of many objects. 78 * 79 * @return <code>true</code> if every object is <code>null</code> or if every object is 80 * non-<code>null</code>. <code>false</code> otherwise. 81 */ 82 public static boolean isHomogeneousSet(Object... objs) { 83 if (objs.length == 0) return true; 84 85 final boolean expectNull = (objs[0] == null); 86 for (Object obj : objs) { 87 if (expectNull ^ (obj == null)) { 88 // xor tells us when the parities differ, which is only when objs[0] was null and 89 // obj is non-null, or objs[0] was non-null and obj is null 90 return false; 91 } 92 } 93 return true; 94 } 95 } 96
