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Diffstat (limited to 'src/org/apache/commons/lang3/ObjectUtils.java')
| -rw-r--r-- | src/org/apache/commons/lang3/ObjectUtils.java | 608 |
1 files changed, 0 insertions, 608 deletions
diff --git a/src/org/apache/commons/lang3/ObjectUtils.java b/src/org/apache/commons/lang3/ObjectUtils.java deleted file mode 100644 index 21de29a..0000000 --- a/src/org/apache/commons/lang3/ObjectUtils.java +++ /dev/null @@ -1,608 +0,0 @@ -/* - * Licensed to the Apache Software Foundation (ASF) under one or more - * contributor license agreements. See the NOTICE file distributed with - * this work for additional information regarding copyright ownership. - * The ASF licenses this file to You 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 org.apache.commons.lang3; - -import java.io.Serializable; -import java.lang.reflect.Array; -import java.lang.reflect.InvocationTargetException; -import java.lang.reflect.Method; -import java.util.Collections; -import java.util.Comparator; -import java.util.HashMap; -import java.util.Map; -import java.util.TreeSet; - -import org.apache.commons.lang3.exception.CloneFailedException; -import org.apache.commons.lang3.mutable.MutableInt; - -/** - * <p>Operations on {@code Object}.</p> - * - * <p>This class tries to handle {@code null} input gracefully. - * An exception will generally not be thrown for a {@code null} input. - * Each method documents its behaviour in more detail.</p> - * - * <p>#ThreadSafe#</p> - * @since 1.0 - * @version $Id: ObjectUtils.java 1153350 2011-08-03 05:29:21Z bayard $ - */ -//@Immutable -public class ObjectUtils { - - /** - * <p>Singleton used as a {@code null} placeholder where - * {@code null} has another meaning.</p> - * - * <p>For example, in a {@code HashMap} the - * {@link java.util.HashMap#get(java.lang.Object)} method returns - * {@code null} if the {@code Map} contains {@code null} or if there - * is no matching key. The {@code Null} placeholder can be used to - * distinguish between these two cases.</p> - * - * <p>Another example is {@code Hashtable}, where {@code null} - * cannot be stored.</p> - * - * <p>This instance is Serializable.</p> - */ - public static final Null NULL = new Null(); - - /** - * <p>{@code ObjectUtils} instances should NOT be constructed in - * standard programming. Instead, the static methods on the class should - * be used, such as {@code ObjectUtils.defaultIfNull("a","b");}.</p> - * - * <p>This constructor is public to permit tools that require a JavaBean - * instance to operate.</p> - */ - public ObjectUtils() { - super(); - } - - // Defaulting - //----------------------------------------------------------------------- - /** - * <p>Returns a default value if the object passed is {@code null}.</p> - * - * <pre> - * ObjectUtils.defaultIfNull(null, null) = null - * ObjectUtils.defaultIfNull(null, "") = "" - * ObjectUtils.defaultIfNull(null, "zz") = "zz" - * ObjectUtils.defaultIfNull("abc", *) = "abc" - * ObjectUtils.defaultIfNull(Boolean.TRUE, *) = Boolean.TRUE - * </pre> - * - * @param <T> the type of the object - * @param object the {@code Object} to test, may be {@code null} - * @param defaultValue the default value to return, may be {@code null} - * @return {@code object} if it is not {@code null}, defaultValue otherwise - */ - public static <T> T defaultIfNull(T object, T defaultValue) { - return object != null ? object : defaultValue; - } - - /** - * <p>Returns the first value in the array which is not {@code null}. - * If all the values are {@code null} or the array is {@code null} - * or empty then {@code null} is returned.</p> - * - * <pre> - * ObjectUtils.firstNonNull(null, null) = null - * ObjectUtils.firstNonNull(null, "") = "" - * ObjectUtils.firstNonNull(null, null, "") = "" - * ObjectUtils.firstNonNull(null, "zz") = "zz" - * ObjectUtils.firstNonNull("abc", *) = "abc" - * ObjectUtils.firstNonNull(null, "xyz", *) = "xyz" - * ObjectUtils.firstNonNull(Boolean.TRUE, *) = Boolean.TRUE - * ObjectUtils.firstNonNull() = null - * </pre> - * - * @param <T> the component type of the array - * @param values the values to test, may be {@code null} or empty - * @return the first value from {@code values} which is not {@code null}, - * or {@code null} if there are no non-null values - * @since 3.0 - */ - public static <T> T firstNonNull(T... values) { - if (values != null) { - for (T val : values) { - if (val != null) { - return val; - } - } - } - return null; - } - - // Null-safe equals/hashCode - //----------------------------------------------------------------------- - /** - * <p>Compares two objects for equality, where either one or both - * objects may be {@code null}.</p> - * - * <pre> - * ObjectUtils.equals(null, null) = true - * ObjectUtils.equals(null, "") = false - * ObjectUtils.equals("", null) = false - * ObjectUtils.equals("", "") = true - * ObjectUtils.equals(Boolean.TRUE, null) = false - * ObjectUtils.equals(Boolean.TRUE, "true") = false - * ObjectUtils.equals(Boolean.TRUE, Boolean.TRUE) = true - * ObjectUtils.equals(Boolean.TRUE, Boolean.FALSE) = false - * </pre> - * - * @param object1 the first object, may be {@code null} - * @param object2 the second object, may be {@code null} - * @return {@code true} if the values of both objects are the same - */ - public static boolean equals(Object object1, Object object2) { - if (object1 == object2) { - return true; - } - if ((object1 == null) || (object2 == null)) { - return false; - } - return object1.equals(object2); - } - - /** - * <p>Compares two objects for inequality, where either one or both - * objects may be {@code null}.</p> - * - * <pre> - * ObjectUtils.notEqual(null, null) = false - * ObjectUtils.notEqual(null, "") = true - * ObjectUtils.notEqual("", null) = true - * ObjectUtils.notEqual("", "") = false - * ObjectUtils.notEqual(Boolean.TRUE, null) = true - * ObjectUtils.notEqual(Boolean.TRUE, "true") = true - * ObjectUtils.notEqual(Boolean.TRUE, Boolean.TRUE) = false - * ObjectUtils.notEqual(Boolean.TRUE, Boolean.FALSE) = true - * </pre> - * - * @param object1 the first object, may be {@code null} - * @param object2 the second object, may be {@code null} - * @return {@code false} if the values of both objects are the same - */ - public static boolean notEqual(Object object1, Object object2) { - return ObjectUtils.equals(object1, object2) == false; - } - - /** - * <p>Gets the hash code of an object returning zero when the - * object is {@code null}.</p> - * - * <pre> - * ObjectUtils.hashCode(null) = 0 - * ObjectUtils.hashCode(obj) = obj.hashCode() - * </pre> - * - * @param obj the object to obtain the hash code of, may be {@code null} - * @return the hash code of the object, or zero if null - * @since 2.1 - */ - public static int hashCode(Object obj) { - // hashCode(Object) retained for performance, as hash code is often critical - return (obj == null) ? 0 : obj.hashCode(); - } - - /** - * <p>Gets the hash code for multiple objects.</p> - * - * <p>This allows a hash code to be rapidly calculated for a number of objects. - * The hash code for a single object is the <em>not</em> same as {@link #hashCode(Object)}. - * The hash code for multiple objects is the same as that calculated by an - * {@code ArrayList} containing the specified objects.</p> - * - * <pre> - * ObjectUtils.hashCodeMulti() = 1 - * ObjectUtils.hashCodeMulti((Object[]) null) = 1 - * ObjectUtils.hashCodeMulti(a) = 31 + a.hashCode() - * ObjectUtils.hashCodeMulti(a,b) = (31 + a.hashCode()) * 31 + b.hashCode() - * ObjectUtils.hashCodeMulti(a,b,c) = ((31 + a.hashCode()) * 31 + b.hashCode()) * 31 + c.hashCode() - * </pre> - * - * @param objects the objects to obtain the hash code of, may be {@code null} - * @return the hash code of the objects, or zero if null - * @since 3.0 - */ - public static int hashCodeMulti(Object... objects) { - int hash = 1; - if (objects != null) { - for (Object object : objects) { - hash = hash * 31 + ObjectUtils.hashCode(object); - } - } - return hash; - } - - // Identity ToString - //----------------------------------------------------------------------- - /** - * <p>Gets the toString that would be produced by {@code Object} - * if a class did not override toString itself. {@code null} - * will return {@code null}.</p> - * - * <pre> - * ObjectUtils.identityToString(null) = null - * ObjectUtils.identityToString("") = "java.lang.String@1e23" - * ObjectUtils.identityToString(Boolean.TRUE) = "java.lang.Boolean@7fa" - * </pre> - * - * @param object the object to create a toString for, may be - * {@code null} - * @return the default toString text, or {@code null} if - * {@code null} passed in - */ - public static String identityToString(Object object) { - if (object == null) { - return null; - } - StringBuffer buffer = new StringBuffer(); - identityToString(buffer, object); - return buffer.toString(); - } - - /** - * <p>Appends the toString that would be produced by {@code Object} - * if a class did not override toString itself. {@code null} - * will throw a NullPointerException for either of the two parameters. </p> - * - * <pre> - * ObjectUtils.identityToString(buf, "") = buf.append("java.lang.String@1e23" - * ObjectUtils.identityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa" - * ObjectUtils.identityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa") - * </pre> - * - * @param buffer the buffer to append to - * @param object the object to create a toString for - * @since 2.4 - */ - public static void identityToString(StringBuffer buffer, Object object) { - if (object == null) { - throw new NullPointerException("Cannot get the toString of a null identity"); - } - buffer.append(object.getClass().getName()) - .append('@') - .append(Integer.toHexString(System.identityHashCode(object))); - } - - // ToString - //----------------------------------------------------------------------- - /** - * <p>Gets the {@code toString} of an {@code Object} returning - * an empty string ("") if {@code null} input.</p> - * - * <pre> - * ObjectUtils.toString(null) = "" - * ObjectUtils.toString("") = "" - * ObjectUtils.toString("bat") = "bat" - * ObjectUtils.toString(Boolean.TRUE) = "true" - * </pre> - * - * @see StringUtils#defaultString(String) - * @see String#valueOf(Object) - * @param obj the Object to {@code toString}, may be null - * @return the passed in Object's toString, or nullStr if {@code null} input - * @since 2.0 - */ - public static String toString(Object obj) { - return obj == null ? "" : obj.toString(); - } - - /** - * <p>Gets the {@code toString} of an {@code Object} returning - * a specified text if {@code null} input.</p> - * - * <pre> - * ObjectUtils.toString(null, null) = null - * ObjectUtils.toString(null, "null") = "null" - * ObjectUtils.toString("", "null") = "" - * ObjectUtils.toString("bat", "null") = "bat" - * ObjectUtils.toString(Boolean.TRUE, "null") = "true" - * </pre> - * - * @see StringUtils#defaultString(String,String) - * @see String#valueOf(Object) - * @param obj the Object to {@code toString}, may be null - * @param nullStr the String to return if {@code null} input, may be null - * @return the passed in Object's toString, or nullStr if {@code null} input - * @since 2.0 - */ - public static String toString(Object obj, String nullStr) { - return obj == null ? nullStr : obj.toString(); - } - - // Comparable - //----------------------------------------------------------------------- - /** - * <p>Null safe comparison of Comparables.</p> - * - * @param <T> type of the values processed by this method - * @param values the set of comparable values, may be null - * @return - * <ul> - * <li>If any objects are non-null and unequal, the lesser object. - * <li>If all objects are non-null and equal, the first. - * <li>If any of the comparables are null, the lesser of the non-null objects. - * <li>If all the comparables are null, null is returned. - * </ul> - */ - public static <T extends Comparable<? super T>> T min(T... values) { - T result = null; - if (values != null) { - for (T value : values) { - if (compare(value, result, true) < 0) { - result = value; - } - } - } - return result; - } - - /** - * <p>Null safe comparison of Comparables.</p> - * - * @param <T> type of the values processed by this method - * @param values the set of comparable values, may be null - * @return - * <ul> - * <li>If any objects are non-null and unequal, the greater object. - * <li>If all objects are non-null and equal, the first. - * <li>If any of the comparables are null, the greater of the non-null objects. - * <li>If all the comparables are null, null is returned. - * </ul> - */ - public static <T extends Comparable<? super T>> T max(T... values) { - T result = null; - if (values != null) { - for (T value : values) { - if (compare(value, result, false) > 0) { - result = value; - } - } - } - return result; - } - - /** - * <p>Null safe comparison of Comparables. - * {@code null} is assumed to be less than a non-{@code null} value.</p> - * - * @param <T> type of the values processed by this method - * @param c1 the first comparable, may be null - * @param c2 the second comparable, may be null - * @return a negative value if c1 < c2, zero if c1 = c2 - * and a positive value if c1 > c2 - */ - public static <T extends Comparable<? super T>> int compare(T c1, T c2) { - return compare(c1, c2, false); - } - - /** - * <p>Null safe comparison of Comparables.</p> - * - * @param <T> type of the values processed by this method - * @param c1 the first comparable, may be null - * @param c2 the second comparable, may be null - * @param nullGreater if true {@code null} is considered greater - * than a non-{@code null} value or if false {@code null} is - * considered less than a Non-{@code null} value - * @return a negative value if c1 < c2, zero if c1 = c2 - * and a positive value if c1 > c2 - * @see java.util.Comparator#compare(Object, Object) - */ - public static <T extends Comparable<? super T>> int compare(T c1, T c2, boolean nullGreater) { - if (c1 == c2) { - return 0; - } else if (c1 == null) { - return (nullGreater ? 1 : -1); - } else if (c2 == null) { - return (nullGreater ? -1 : 1); - } - return c1.compareTo(c2); - } - - /** - * Find the "best guess" middle value among comparables. If there is an even - * number of total values, the lower of the two middle values will be returned. - * @param <T> type of values processed by this method - * @param items to compare - * @return T at middle position - * @throws NullPointerException if items is {@code null} - * @throws IllegalArgumentException if items is empty or contains {@code null} values - * @since 3.0.1 - */ - public static <T extends Comparable<? super T>> T median(T... items) { - Validate.notEmpty(items); - Validate.noNullElements(items); - TreeSet<T> sort = new TreeSet<T>(); - Collections.addAll(sort, items); - @SuppressWarnings("unchecked") //we know all items added were T instances - T result = (T) sort.toArray()[(sort.size() - 1) / 2]; - return result; - } - - /** - * Find the "best guess" middle value among comparables. If there is an even - * number of total values, the lower of the two middle values will be returned. - * @param <T> type of values processed by this method - * @param comparator to use for comparisons - * @param items to compare - * @return T at middle position - * @throws NullPointerException if items or comparator is {@code null} - * @throws IllegalArgumentException if items is empty or contains {@code null} values - * @since 3.0.1 - */ - public static <T> T median(Comparator<T> comparator, T... items) { - Validate.notEmpty(items, "null/empty items"); - Validate.noNullElements(items); - Validate.notNull(comparator, "null comparator"); - TreeSet<T> sort = new TreeSet<T>(comparator); - Collections.addAll(sort, items); - @SuppressWarnings("unchecked") //we know all items added were T instances - T result = (T) sort.toArray()[(sort.size() - 1) / 2]; - return result; - } - - // Mode - //----------------------------------------------------------------------- - /** - * Find the most frequently occurring item. - * - * @param <T> type of values processed by this method - * @param items to check - * @return most populous T, {@code null} if non-unique or no items supplied - * @since 3.0.1 - */ - public static <T> T mode(T... items) { - if (ArrayUtils.isNotEmpty(items)) { - HashMap<T, MutableInt> occurrences = new HashMap<T, MutableInt>(items.length); - for (T t : items) { - MutableInt count = occurrences.get(t); - if (count == null) { - occurrences.put(t, new MutableInt(1)); - } else { - count.increment(); - } - } - T result = null; - int max = 0; - for (Map.Entry<T, MutableInt> e : occurrences.entrySet()) { - int cmp = e.getValue().intValue(); - if (cmp == max) { - result = null; - } else if (cmp > max) { - max = cmp; - result = e.getKey(); - } - } - return result; - } - return null; - } - - // cloning - //----------------------------------------------------------------------- - /** - * <p>Clone an object.</p> - * - * @param <T> the type of the object - * @param obj the object to clone, null returns null - * @return the clone if the object implements {@link Cloneable} otherwise {@code null} - * @throws CloneFailedException if the object is cloneable and the clone operation fails - * @since 3.0 - */ - public static <T> T clone(final T obj) { - if (obj instanceof Cloneable) { - final Object result; - if (obj.getClass().isArray()) { - final Class<?> componentType = obj.getClass().getComponentType(); - if (!componentType.isPrimitive()) { - result = ((Object[]) obj).clone(); - } else { - int length = Array.getLength(obj); - result = Array.newInstance(componentType, length); - while (length-- > 0) { - Array.set(result, length, Array.get(obj, length)); - } - } - } else { - try { - final Method clone = obj.getClass().getMethod("clone"); - result = clone.invoke(obj); - } catch (final NoSuchMethodException e) { - throw new CloneFailedException("Cloneable type " - + obj.getClass().getName() - + " has no clone method", e); - } catch (final IllegalAccessException e) { - throw new CloneFailedException("Cannot clone Cloneable type " - + obj.getClass().getName(), e); - } catch (final InvocationTargetException e) { - throw new CloneFailedException("Exception cloning Cloneable type " - + obj.getClass().getName(), e.getCause()); - } - } - @SuppressWarnings("unchecked") - final T checked = (T) result; - return checked; - } - - return null; - } - - /** - * <p>Clone an object if possible.</p> - * - * <p>This method is similar to {@link #clone(Object)}, but will return the provided - * instance as the return value instead of {@code null} if the instance - * is not cloneable. This is more convenient if the caller uses different - * implementations (e.g. of a service) and some of the implementations do not allow concurrent - * processing or have state. In such cases the implementation can simply provide a proper - * clone implementation and the caller's code does not have to change.</p> - * - * @param <T> the type of the object - * @param obj the object to clone, null returns null - * @return the clone if the object implements {@link Cloneable} otherwise the object itself - * @throws CloneFailedException if the object is cloneable and the clone operation fails - * @since 3.0 - */ - public static <T> T cloneIfPossible(final T obj) { - final T clone = clone(obj); - return clone == null ? obj : clone; - } - - // Null - //----------------------------------------------------------------------- - /** - * <p>Class used as a null placeholder where {@code null} - * has another meaning.</p> - * - * <p>For example, in a {@code HashMap} the - * {@link java.util.HashMap#get(java.lang.Object)} method returns - * {@code null} if the {@code Map} contains {@code null} or if there is - * no matching key. The {@code Null} placeholder can be used to distinguish - * between these two cases.</p> - * - * <p>Another example is {@code Hashtable}, where {@code null} - * cannot be stored.</p> - */ - public static class Null implements Serializable { - /** - * Required for serialization support. Declare serialization compatibility with Commons Lang 1.0 - * - * @see java.io.Serializable - */ - private static final long serialVersionUID = 7092611880189329093L; - - /** - * Restricted constructor - singleton. - */ - Null() { - super(); - } - - /** - * <p>Ensure singleton.</p> - * - * @return the singleton value - */ - private Object readResolve() { - return ObjectUtils.NULL; - } - } - -} |