1 | /*
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2 | * Licensed to the Apache Software Foundation (ASF) under one or more
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3 | * contributor license agreements. See the NOTICE file distributed with
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4 | * this work for additional information regarding copyright ownership.
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5 | * The ASF licenses this file to You under the Apache License, Version 2.0
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6 | * (the "License"); you may not use this file except in compliance with
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7 | * the License. You may obtain a copy of the License at
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8 | *
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9 | * http://www.apache.org/licenses/LICENSE-2.0
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10 | *
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11 | * Unless required by applicable law or agreed to in writing, software
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12 | * distributed under the License is distributed on an "AS IS" BASIS,
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13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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14 | * See the License for the specific language governing permissions and
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15 | * limitations under the License.
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16 | */
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17 | package agents.org.apache.commons.lang;
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18 |
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19 | import java.io.Serializable;
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20 | import java.lang.reflect.Array;
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21 | import java.lang.reflect.InvocationTargetException;
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22 |
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23 | import agents.org.apache.commons.lang.exception.CloneFailedException;
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24 | import agents.org.apache.commons.lang.reflect.MethodUtils;
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25 |
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26 | /**
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27 | * <p>Operations on <code>Object</code>.</p>
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28 | *
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29 | * <p>This class tries to handle <code>null</code> input gracefully.
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30 | * An exception will generally not be thrown for a <code>null</code> input.
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31 | * Each method documents its behaviour in more detail.</p>
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32 | *
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33 | * <p>#ThreadSafe#</p>
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34 | * @author Apache Software Foundation
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35 | * @author <a href="mailto:nissim@nksystems.com">Nissim Karpenstein</a>
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36 | * @author <a href="mailto:janekdb@yahoo.co.uk">Janek Bogucki</a>
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37 | * @author Daniel L. Rall
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38 | * @author Gary Gregory
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39 | * @author Mario Winterer
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40 | * @author <a href="mailto:david@davidkarlsen.com">David J. M. Karlsen</a>
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41 | * @since 1.0
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42 | * @version $Id: ObjectUtils.java 1057434 2011-01-11 01:27:37Z niallp $
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43 | */
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44 | //@Immutable
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45 | public class ObjectUtils {
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46 |
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47 | /**
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48 | * <p>Singleton used as a <code>null</code> placeholder where
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49 | * <code>null</code> has another meaning.</p>
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50 | *
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51 | * <p>For example, in a <code>HashMap</code> the
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52 | * {@link java.util.HashMap#get(java.lang.Object)} method returns
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53 | * <code>null</code> if the <code>Map</code> contains
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54 | * <code>null</code> or if there is no matching key. The
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55 | * <code>Null</code> placeholder can be used to distinguish between
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56 | * these two cases.</p>
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57 | *
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58 | * <p>Another example is <code>Hashtable</code>, where <code>null</code>
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59 | * cannot be stored.</p>
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60 | *
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61 | * <p>This instance is Serializable.</p>
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62 | */
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63 | public static final Null NULL = new Null();
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64 |
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65 | /**
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66 | * <p><code>ObjectUtils</code> instances should NOT be constructed in
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67 | * standard programming. Instead, the class should be used as
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68 | * <code>ObjectUtils.defaultIfNull("a","b");</code>.</p>
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69 | *
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70 | * <p>This constructor is public to permit tools that require a JavaBean instance
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71 | * to operate.</p>
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72 | */
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73 | public ObjectUtils() {
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74 | super();
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75 | }
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76 |
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77 | // Defaulting
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78 | //-----------------------------------------------------------------------
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79 | /**
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80 | * <p>Returns a default value if the object passed is
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81 | * <code>null</code>.</p>
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82 | *
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83 | * <pre>
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84 | * ObjectUtils.defaultIfNull(null, null) = null
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85 | * ObjectUtils.defaultIfNull(null, "") = ""
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86 | * ObjectUtils.defaultIfNull(null, "zz") = "zz"
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87 | * ObjectUtils.defaultIfNull("abc", *) = "abc"
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88 | * ObjectUtils.defaultIfNull(Boolean.TRUE, *) = Boolean.TRUE
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89 | * </pre>
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90 | *
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91 | * @param object the <code>Object</code> to test, may be <code>null</code>
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92 | * @param defaultValue the default value to return, may be <code>null</code>
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93 | * @return <code>object</code> if it is not <code>null</code>, defaultValue otherwise
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94 | */
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95 | public static Object defaultIfNull(Object object, Object defaultValue) {
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96 | return object != null ? object : defaultValue;
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97 | }
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98 |
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99 | /**
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100 | * <p>Compares two objects for equality, where either one or both
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101 | * objects may be <code>null</code>.</p>
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102 | *
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103 | * <pre>
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104 | * ObjectUtils.equals(null, null) = true
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105 | * ObjectUtils.equals(null, "") = false
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106 | * ObjectUtils.equals("", null) = false
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107 | * ObjectUtils.equals("", "") = true
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108 | * ObjectUtils.equals(Boolean.TRUE, null) = false
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109 | * ObjectUtils.equals(Boolean.TRUE, "true") = false
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110 | * ObjectUtils.equals(Boolean.TRUE, Boolean.TRUE) = true
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111 | * ObjectUtils.equals(Boolean.TRUE, Boolean.FALSE) = false
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112 | * </pre>
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113 | *
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114 | * @param object1 the first object, may be <code>null</code>
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115 | * @param object2 the second object, may be <code>null</code>
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116 | * @return <code>true</code> if the values of both objects are the same
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117 | */
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118 | public static boolean equals(Object object1, Object object2) {
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119 | if (object1 == object2) {
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120 | return true;
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121 | }
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122 | if ((object1 == null) || (object2 == null)) {
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123 | return false;
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124 | }
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125 | return object1.equals(object2);
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126 | }
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127 |
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128 | /**
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129 | * <p>Compares two objects for inequality, where either one or both
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130 | * objects may be <code>null</code>.</p>
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131 | *
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132 | * <pre>
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133 | * ObjectUtils.notEqual(null, null) = false
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134 | * ObjectUtils.notEqual(null, "") = true
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135 | * ObjectUtils.notEqual("", null) = true
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136 | * ObjectUtils.notEqual("", "") = false
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137 | * ObjectUtils.notEqual(Boolean.TRUE, null) = true
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138 | * ObjectUtils.notEqual(Boolean.TRUE, "true") = true
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139 | * ObjectUtils.notEqual(Boolean.TRUE, Boolean.TRUE) = false
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140 | * ObjectUtils.notEqual(Boolean.TRUE, Boolean.FALSE) = true
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141 | * </pre>
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142 | *
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143 | * @param object1 the first object, may be <code>null</code>
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144 | * @param object2 the second object, may be <code>null</code>
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145 | * @return <code>false</code> if the values of both objects are the same
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146 | * @since 2.6
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147 | */
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148 | public static boolean notEqual(Object object1, Object object2) {
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149 | return ObjectUtils.equals(object1, object2) == false;
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150 | }
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151 |
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152 | /**
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153 | * <p>Gets the hash code of an object returning zero when the
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154 | * object is <code>null</code>.</p>
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155 | *
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156 | * <pre>
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157 | * ObjectUtils.hashCode(null) = 0
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158 | * ObjectUtils.hashCode(obj) = obj.hashCode()
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159 | * </pre>
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160 | *
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161 | * @param obj the object to obtain the hash code of, may be <code>null</code>
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162 | * @return the hash code of the object, or zero if null
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163 | * @since 2.1
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164 | */
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165 | public static int hashCode(Object obj) {
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166 | return (obj == null) ? 0 : obj.hashCode();
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167 | }
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168 |
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169 | // Identity ToString
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170 | //-----------------------------------------------------------------------
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171 | /**
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172 | * <p>Gets the toString that would be produced by <code>Object</code>
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173 | * if a class did not override toString itself. <code>null</code>
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174 | * will return <code>null</code>.</p>
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175 | *
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176 | * <pre>
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177 | * ObjectUtils.identityToString(null) = null
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178 | * ObjectUtils.identityToString("") = "java.lang.String@1e23"
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179 | * ObjectUtils.identityToString(Boolean.TRUE) = "java.lang.Boolean@7fa"
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180 | * </pre>
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181 | *
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182 | * @param object the object to create a toString for, may be
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183 | * <code>null</code>
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184 | * @return the default toString text, or <code>null</code> if
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185 | * <code>null</code> passed in
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186 | */
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187 | public static String identityToString(Object object) {
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188 | if (object == null) {
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189 | return null;
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190 | }
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191 | StringBuffer buffer = new StringBuffer();
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192 | identityToString(buffer, object);
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193 | return buffer.toString();
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194 | }
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195 |
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196 | /**
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197 | * <p>Appends the toString that would be produced by <code>Object</code>
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198 | * if a class did not override toString itself. <code>null</code>
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199 | * will throw a NullPointerException for either of the two parameters. </p>
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200 | *
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201 | * <pre>
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202 | * ObjectUtils.identityToString(buf, "") = buf.append("java.lang.String@1e23"
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203 | * ObjectUtils.identityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa"
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204 | * ObjectUtils.identityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa")
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205 | * </pre>
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206 | *
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207 | * @param buffer the buffer to append to
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208 | * @param object the object to create a toString for
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209 | * @since 2.4
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210 | */
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211 | public static void identityToString(StringBuffer buffer, Object object) {
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212 | if (object == null) {
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213 | throw new NullPointerException("Cannot get the toString of a null identity");
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214 | }
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215 | buffer.append(object.getClass().getName())
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216 | .append('@')
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217 | .append(Integer.toHexString(System.identityHashCode(object)));
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218 | }
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219 |
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220 | /**
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221 | * <p>Appends the toString that would be produced by <code>Object</code>
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222 | * if a class did not override toString itself. <code>null</code>
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223 | * will return <code>null</code>.</p>
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224 | *
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225 | * <pre>
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226 | * ObjectUtils.appendIdentityToString(*, null) = null
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227 | * ObjectUtils.appendIdentityToString(null, "") = "java.lang.String@1e23"
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228 | * ObjectUtils.appendIdentityToString(null, Boolean.TRUE) = "java.lang.Boolean@7fa"
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229 | * ObjectUtils.appendIdentityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa")
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230 | * </pre>
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231 | *
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232 | * @param buffer the buffer to append to, may be <code>null</code>
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233 | * @param object the object to create a toString for, may be <code>null</code>
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234 | * @return the default toString text, or <code>null</code> if
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235 | * <code>null</code> passed in
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236 | * @since 2.0
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237 | * @deprecated The design of this method is bad - see LANG-360. Instead, use identityToString(StringBuffer, Object).
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238 | */
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239 | public static StringBuffer appendIdentityToString(StringBuffer buffer, Object object) {
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240 | if (object == null) {
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241 | return null;
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242 | }
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243 | if (buffer == null) {
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244 | buffer = new StringBuffer();
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245 | }
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246 | return buffer
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247 | .append(object.getClass().getName())
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248 | .append('@')
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249 | .append(Integer.toHexString(System.identityHashCode(object)));
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250 | }
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251 |
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252 | // ToString
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253 | //-----------------------------------------------------------------------
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254 | /**
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255 | * <p>Gets the <code>toString</code> of an <code>Object</code> returning
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256 | * an empty string ("") if <code>null</code> input.</p>
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257 | *
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258 | * <pre>
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259 | * ObjectUtils.toString(null) = ""
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260 | * ObjectUtils.toString("") = ""
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261 | * ObjectUtils.toString("bat") = "bat"
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262 | * ObjectUtils.toString(Boolean.TRUE) = "true"
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263 | * </pre>
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264 | *
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265 | * @see StringUtils#defaultString(String)
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266 | * @see String#valueOf(Object)
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267 | * @param obj the Object to <code>toString</code>, may be null
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268 | * @return the passed in Object's toString, or nullStr if <code>null</code> input
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269 | * @since 2.0
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270 | */
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271 | public static String toString(Object obj) {
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272 | return obj == null ? "" : obj.toString();
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273 | }
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274 |
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275 | /**
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276 | * <p>Gets the <code>toString</code> of an <code>Object</code> returning
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277 | * a specified text if <code>null</code> input.</p>
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278 | *
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279 | * <pre>
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280 | * ObjectUtils.toString(null, null) = null
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281 | * ObjectUtils.toString(null, "null") = "null"
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282 | * ObjectUtils.toString("", "null") = ""
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283 | * ObjectUtils.toString("bat", "null") = "bat"
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284 | * ObjectUtils.toString(Boolean.TRUE, "null") = "true"
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285 | * </pre>
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286 | *
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287 | * @see StringUtils#defaultString(String,String)
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288 | * @see String#valueOf(Object)
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289 | * @param obj the Object to <code>toString</code>, may be null
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290 | * @param nullStr the String to return if <code>null</code> input, may be null
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291 | * @return the passed in Object's toString, or nullStr if <code>null</code> input
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292 | * @since 2.0
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293 | */
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294 | public static String toString(Object obj, String nullStr) {
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295 | return obj == null ? nullStr : obj.toString();
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296 | }
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297 |
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298 | // Min/Max
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299 | //-----------------------------------------------------------------------
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300 | /**
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301 | * Null safe comparison of Comparables.
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302 | *
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303 | * @param c1 the first comparable, may be null
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304 | * @param c2 the second comparable, may be null
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305 | * @return
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306 | * <ul>
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307 | * <li>If both objects are non-null and unequal, the lesser object.
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308 | * <li>If both objects are non-null and equal, c1.
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309 | * <li>If one of the comparables is null, the non-null object.
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310 | * <li>If both the comparables are null, null is returned.
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311 | * </ul>
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312 | */
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313 | public static Object min(Comparable c1, Comparable c2) {
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314 | return (compare(c1, c2, true) <= 0 ? c1 : c2);
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315 | }
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316 |
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317 | /**
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318 | * Null safe comparison of Comparables.
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319 | *
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320 | * @param c1 the first comparable, may be null
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321 | * @param c2 the second comparable, may be null
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322 | * @return
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323 | * <ul>
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324 | * <li>If both objects are non-null and unequal, the greater object.
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325 | * <li>If both objects are non-null and equal, c1.
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326 | * <li>If one of the comparables is null, the non-null object.
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327 | * <li>If both the comparables are null, null is returned.
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328 | * </ul>
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329 | */
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330 | public static Object max(Comparable c1, Comparable c2) {
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331 | return (compare(c1, c2, false) >= 0 ? c1 : c2);
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332 | }
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333 |
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334 | /**
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335 | * Null safe comparison of Comparables.
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336 | * {@code null} is assumed to be less than a non-{@code null} value.
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337 | *
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338 | * @param c1 the first comparable, may be null
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339 | * @param c2 the second comparable, may be null
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340 | * @return a negative value if c1 < c2, zero if c1 = c2
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341 | * and a positive value if c1 > c2
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342 | * @since 2.6
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343 | */
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344 | public static int compare(Comparable c1, Comparable c2) {
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345 | return compare(c1, c2, false);
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346 | }
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347 |
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348 | /**
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349 | * Null safe comparison of Comparables.
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350 | *
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351 | * @param c1 the first comparable, may be null
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352 | * @param c2 the second comparable, may be null
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353 | * @param nullGreater if true <code>null</code> is considered greater
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354 | * than a Non-<code>null</code> value or if false <code>null</code> is
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355 | * considered less than a Non-<code>null</code> value
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356 | * @return a negative value if c1 < c2, zero if c1 = c2
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357 | * and a positive value if c1 > c2
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358 | * @see java.util.Comparator#compare(Object, Object)
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359 | * @since 2.6
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360 | */
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361 | public static int compare(Comparable c1, Comparable c2, boolean nullGreater) {
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362 | if (c1 == c2) {
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363 | return 0;
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364 | } else if (c1 == null) {
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365 | return (nullGreater ? 1 : -1);
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366 | } else if (c2 == null) {
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367 | return (nullGreater ? -1 : 1);
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368 | }
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369 | return c1.compareTo(c2);
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370 | }
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371 |
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372 | /**
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373 | * Clone an object.
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374 | *
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375 | * @param o the object to clone
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376 | * @return the clone if the object implements {@link Cloneable} otherwise <code>null</code>
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377 | * @throws CloneFailedException if the object is cloneable and the clone operation fails
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378 | * @since 2.6
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379 | */
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380 | public static Object clone(final Object o) {
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381 | if (o instanceof Cloneable) {
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382 | final Object result;
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383 | if (o.getClass().isArray()) {
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384 | final Class componentType = o.getClass().getComponentType();
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385 | if (!componentType.isPrimitive()) {
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386 | result = ((Object[])o).clone();
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387 | } else {
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388 | int length = Array.getLength(o);
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389 | result = Array.newInstance(componentType, length);
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390 | while (length-- > 0) {
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391 | Array.set(result, length, Array.get(o, length));
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392 | }
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393 | }
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394 | } else {
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395 | try {
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396 | result = MethodUtils.invokeMethod(o, "clone", null);
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397 | } catch (final NoSuchMethodException e) {
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398 | throw new CloneFailedException("Cloneable type "
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399 | + o.getClass().getName()
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400 | + " has no clone method", e);
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401 | } catch (final IllegalAccessException e) {
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402 | throw new CloneFailedException("Cannot clone Cloneable type "
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403 | + o.getClass().getName(), e);
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404 | } catch (final InvocationTargetException e) {
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405 | throw new CloneFailedException("Exception cloning Cloneable type "
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406 | + o.getClass().getName(), e.getTargetException());
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407 | }
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408 | }
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409 | return result;
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410 | }
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411 |
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412 | return null;
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413 | }
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414 |
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415 | /**
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416 | * Clone an object if possible. This method is similar to {@link #clone(Object)}, but will
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417 | * return the provided instance as the return value instead of <code>null</code> if the instance
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418 | * is not cloneable. This is more convenient if the caller uses different
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419 | * implementations (e.g. of a service) and some of the implementations do not allow concurrent
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420 | * processing or have state. In such cases the implementation can simply provide a proper
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421 | * clone implementation and the caller's code does not have to change.
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422 | *
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423 | * @param o the object to clone
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424 | * @return the clone if the object implements {@link Cloneable} otherwise the object itself
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425 | * @throws CloneFailedException if the object is cloneable and the clone operation fails
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426 | * @since 2.6
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427 | */
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428 | public static Object cloneIfPossible(final Object o) {
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429 | final Object clone = clone(o);
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430 | return clone == null ? o : clone;
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431 | }
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432 |
|
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433 | // Null
|
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434 | //-----------------------------------------------------------------------
|
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435 | /**
|
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436 | * <p>Class used as a null placeholder where <code>null</code>
|
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437 | * has another meaning.</p>
|
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438 | *
|
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439 | * <p>For example, in a <code>HashMap</code> the
|
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440 | * {@link java.util.HashMap#get(java.lang.Object)} method returns
|
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441 | * <code>null</code> if the <code>Map</code> contains
|
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442 | * <code>null</code> or if there is no matching key. The
|
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443 | * <code>Null</code> placeholder can be used to distinguish between
|
---|
444 | * these two cases.</p>
|
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445 | *
|
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446 | * <p>Another example is <code>Hashtable</code>, where <code>null</code>
|
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447 | * cannot be stored.</p>
|
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448 | */
|
---|
449 | public static class Null implements Serializable {
|
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450 | /**
|
---|
451 | * Required for serialization support. Declare serialization compatibility with Commons Lang 1.0
|
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452 | *
|
---|
453 | * @see java.io.Serializable
|
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454 | */
|
---|
455 | private static final long serialVersionUID = 7092611880189329093L;
|
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456 |
|
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457 | /**
|
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458 | * Restricted constructor - singleton.
|
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459 | */
|
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460 | Null() {
|
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461 | super();
|
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462 | }
|
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463 |
|
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464 | /**
|
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465 | * <p>Ensure singleton.</p>
|
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466 | *
|
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467 | * @return the singleton value
|
---|
468 | */
|
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469 | private Object readResolve() {
|
---|
470 | return ObjectUtils.NULL;
|
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471 | }
|
---|
472 | }
|
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473 |
|
---|
474 | }
|
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